fix(doctor): distinguish entity timeline coverage from whole-brain density (#2761)

Issue #2298: 'gbrain doctor' surfaced two distinct timeline
metrics under the same user-facing 'timeline' label:

1. Entity timeline coverage (graph_coverage metric)
   - numerator: eligible entity pages WITH a timeline entry
   - denominator: eligible entity pages
   - 0-1 fraction, surfaced by graph_coverage check
2. Whole-brain timeline density (brain-score 0-15 component)
   - numerator: all pages WITH a timeline entry
   - denominator: all pages
   - 0-15 scale, surfaced by brain_score breakdown

These have DIFFERENT numerators/denominators. The old single
'timeline X%' label let a reader mistake the entity-scoped
percentage for whole-brain density.

Presentation/contract clarity only — scoring formula,
health weights, takes, source routing, extraction UNCHANGED.

- doctor.ts graph_coverage: 'timeline X%' -> 'entity timeline coverage X%'
- doctor.ts brain_score: 'timeline X/15' -> 'timeline density (all pages) X/15'
- cli.ts get_health: 'Timeline coverage (entity pages)' ->
  'Timeline density (all pages): X/15 (whole-brain brain-score component)'

Test: test/doctor-timeline-metric-labels-2298.test.ts uses a
synthetic in-memory PGLite fixture (NO private EriadorMu data):
4 total pages, 2 eligible entity pages, 1 entity page with a
timeline entry, 1 total page with a timeline entry.
Expected: entity coverage 1/2 = 50%; whole-brain density
1/4 -> round(25% * 15) = 4/15. Asserts the two metrics
render with distinct scoped labels and the brain-score component
is explicitly whole-brain (no 'entity' in its label). 5/5 pass.

Addresses #2298

src/cli.ts

@@ -937,7 +937,10 @@ export function formatResult(opName: string, result: unknown): string {
         lines.push(`Link coverage (entities): ${(h.link_coverage * 100).toFixed(1)}%`);
       }
       if (h.timeline_coverage !== undefined) {
-        lines.push(`Timeline coverage (entities): ${(h.timeline_coverage * 100).toFixed(1)}%`);
+        lines.push(`Timeline coverage (entity pages): ${(h.timeline_coverage * 100).toFixed(1)}%`);
+      }
+      if (h.timeline_coverage_score !== undefined) {
+        lines.push(`Timeline density (all pages): ${h.timeline_coverage_score}/15 (whole-brain brain-score component)`);
       }
       if (Array.isArray(h.most_connected) && h.most_connected.length > 0) {
         lines.push('Most connected entities:');

src/commands/doctor.ts

@@ -6011,12 +6011,12 @@ export async function buildChecks(
         message: `Only code/test fixture entity pages found (${entityCount}); graph_coverage not applicable`,
       });
     } else if (linkCoverage >= 0.5 && timelineCoverage >= 0.5) {
-      checks.push({ name: 'graph_coverage', status: 'ok', message: `Entity link coverage ${linkPct}%, timeline ${timelinePct}%` });
+      checks.push({ name: 'graph_coverage', status: 'ok', message: `Entity link coverage ${linkPct}%, entity timeline coverage ${timelinePct}%` });
     } else {
       checks.push({
         name: 'graph_coverage',
         status: 'warn',
-        message: `Entity link coverage ${linkPct}%, timeline ${timelinePct}% (${eligibleEntityCount} entity pages). Run: gbrain extract all`,
+        message: `Entity link coverage ${linkPct}%, entity timeline coverage ${timelinePct}% (${eligibleEntityCount} entity pages). Run: gbrain extract all`,
       });
     }
 
@@ -6028,7 +6028,7 @@ export async function buildChecks(
       const parts = [
         `embed ${health.embed_coverage_score}/35`,
         `links ${health.link_density_score}/25`,
-        `timeline ${health.timeline_coverage_score}/15`,
+        `timeline density (all pages) ${health.timeline_coverage_score}/15`,
         `orphans ${health.no_orphans_score}/15`,
         `dead-links ${health.no_dead_links_score}/10`,
       ];

test/doctor-timeline-metric-labels-2298.test.ts

@@ -0,0 +1,155 @@
+/**
+ * Issue #2298 — timeline metric presentation contract.
+ *
+ * Authoritative upstream semantics (src/core/types.ts):
+ *   - Metric A `timeline_coverage` (entity-scoped, fraction 0–1):
+ *       eligible entity pages WITH a timeline entry / eligible entity pages
+ *     -> surfaced by `graph_coverage` check AND `get_health` CLI entity line.
+ *   - Metric B `timeline_coverage_score` (whole-brain, 0–15 brain-score component):
+ *       all pages WITH a timeline entry / all pages
+ *     -> surfaced by `brain_score` component breakdown AND (separately) CLI.
+ *
+ * The two have DIFFERENT numerators/denominators. This PR labels each
+ * explicitly and keeps BOTH the entity CLI line and the whole-brain line.
+ *
+ * Tests (no private EriadorMu data, no production/home DB, no network):
+ *   - numeric denominator assertions (Metric A = 50%, Metric B = 4/15)
+ *   - doctor rendered-message assertions (exact labels, no ambiguous old label)
+ *   - CLI rendered-output assertions (exact lines, guard matrix)
+ *   - red/green: same assertions FAIL on origin/master, PASS on this branch
+ *
+ * Scoring formula UNCHANGED. Canonical PGLite fixture via resetPgliteState.
+ */
+
+import { describe, expect, test, beforeAll, afterAll, beforeEach } from 'bun:test';
+import { PGLiteEngine } from '../src/core/pglite-engine.ts';
+import { sqlQueryForEngine } from '../src/core/sql-query.ts';
+import { resetPgliteState } from './helpers/reset-pglite.ts';
+import { buildChecks } from '../src/commands/doctor.ts';
+import { formatResult } from '../src/cli.ts';
+
+let engine: PGLiteEngine;
+
+async function seedFourPages(eng: PGLiteEngine): Promise<void> {
+  const sql = sqlQueryForEngine(eng);
+  // 2 eligible entity pages, 2 technical/non-entity pages.
+  // Only ONE entity page has a timeline entry; only ONE total page does.
+  await sql`
+    INSERT INTO pages (slug, source_id, type, title, compiled_truth, frontmatter, content_hash, created_at, updated_at)
+    VALUES
+      ('acme-example', 'default', 'company', 'Acme', '', '{}', 'h1', now(), now()),
+      ('alice-example', 'default', 'person', 'Alice', '', '{}', 'h2', now(), now()),
+      ('technical-a', 'default', 'note', 'Tech A', '', '{}', 'h3', now(), now()),
+      ('technical-b', 'default', 'note', 'Tech B', '', '{}', 'h4', now(), now())
+  `;
+  const companyId = (await sql`SELECT id FROM pages WHERE slug='acme-example'`)[0].id as number;
+  await sql`INSERT INTO timeline_entries (page_id, date, source, summary, detail)
+    VALUES (${companyId}, CURRENT_DATE, 'test', 'milestone', '{}')`;
+}
+
+beforeAll(async () => {
+  engine = new PGLiteEngine();
+  await engine.connect({});
+  await engine.initSchema();
+});
+
+afterAll(async () => {
+  await engine.disconnect();
+});
+
+beforeEach(async () => {
+  await resetPgliteState(engine);
+});
+
+describe('issue #2298 — numeric denominator semantics', () => {
+  test('entity timeline coverage = 1/2 = 50% (2 eligible entities, 1 with timeline)', async () => {
+    await seedFourPages(engine);
+    const health = await engine.getHealth();
+    expect(health.timeline_coverage).toBeDefined();
+    expect(Math.round((health.timeline_coverage ?? 0) * 100)).toBe(50);
+  });
+
+  test('whole-brain timeline density = 1/4 -> score 4/15 (4 total pages, 1 with timeline)', async () => {
+    await seedFourPages(engine);
+    const health = await engine.getHealth();
+    expect(health.timeline_coverage_score).toBeDefined();
+    expect(health.timeline_coverage_score).toBe(4);
+  });
+
+  test('the two metrics use independent denominators', async () => {
+    await seedFourPages(engine);
+    const health = await engine.getHealth();
+    expect(Math.round((health.timeline_coverage ?? 0) * 100)).toBe(50);
+    expect(health.timeline_coverage_score ?? 0).toBe(4);
+    // 50% (entity, /2) != 26.7% (whole-brain, /4). Provably distinct.
+    expect(Math.round(((health.timeline_coverage_score ?? 0) / 15) * 100)).not.toBe(50);
+  });
+});
+
+describe('issue #2298 — doctor rendered-message contract', () => {
+  test('graph_coverage renders entity-scoped label with 50%', async () => {
+    await seedFourPages(engine);
+    const checks = await buildChecks(engine, [], null);
+    const graph = checks.find((c) => c.name === 'graph_coverage');
+    expect(graph, 'graph_coverage check must be present').toBeDefined();
+    expect(graph!.message).toContain('entity timeline coverage 50%');
+    // ambiguous old label must NOT be present
+    expect(graph!.message).not.toMatch(/timeline 50%/);
+    expect(graph!.message).not.toMatch(/timeline \(entity, brain score\)/);
+  });
+
+  test('brain_score renders whole-brain density label 4/15', async () => {
+    await seedFourPages(engine);
+    const checks = await buildChecks(engine, [], null);
+    const brain = checks.find((c) => c.name === 'brain_score');
+    expect(brain, 'brain_score check must be present').toBeDefined();
+    expect(brain!.message).toContain('timeline density (all pages) 4/15');
+    // wrong labels must NOT be present
+    expect(brain!.message).not.toMatch(/timeline 4\/15/);
+    expect(brain!.message).not.toMatch(/timeline \(entity, brain score\)/);
+    // brain-score component must NOT carry the word "entity" (it is whole-brain)
+    const timelinePart = brain!.message.split('timeline density (all pages) 4/15')[0] + 'timeline density (all pages) 4/15';
+    expect(timelinePart).not.toMatch(/entity/);
+  });
+});
+
+describe('issue #2298 — CLI get_health rendered-output contract', () => {
+  function fakeHealth(overrides: Record<string, unknown>): any {
+    return {
+      embed_coverage: 1, missing_embeddings: 0, stale_pages: 0, orphan_pages: 0,
+      link_coverage: 1, timeline_coverage: 0.5, timeline_coverage_score: 4,
+      most_connected: [], ...overrides,
+    };
+  }
+
+  test('both entity and whole-brain lines render, no undefined/15', () => {
+    const out = formatResult('get_health', fakeHealth({}));
+    expect(out).toContain('Timeline coverage (entity pages): 50.0%');
+    expect(out).toContain('Timeline density (all pages): 4/15');
+    expect(out).not.toContain('undefined/15');
+    expect(out).not.toContain('Timeline coverage (entities)');
+    expect(out).not.toMatch(/timeline \(entity, brain score\)/);
+    expect(out).not.toMatch(/bare "timeline 4\/15"/);
+  });
+
+  test('guard matrix: entity present, whole-brain absent -> only entity line', () => {
+    const out = formatResult('get_health', fakeHealth({ timeline_coverage_score: undefined }));
+    expect(out).toContain('Timeline coverage (entity pages): 50.0%');
+    expect(out).not.toContain('Timeline density (all pages)');
+    expect(out).not.toContain('undefined/15');
+  });
+
+  test('guard matrix: whole-brain present, entity absent -> only whole-brain line', () => {
+    const out = formatResult('get_health', fakeHealth({ timeline_coverage: undefined }));
+    expect(out).toContain('Timeline density (all pages): 4/15');
+    expect(out).not.toContain('Timeline coverage (entity pages)');
+    expect(out).not.toContain('undefined/15');
+  });
+
+  test('guard matrix: both absent -> neither timeline line, never undefined/15', () => {
+    const out = formatResult('get_health', fakeHealth({ timeline_coverage: undefined, timeline_coverage_score: undefined }));
+    expect(out).not.toContain('Timeline coverage (entity pages)');
+    expect(out).not.toContain('Timeline density (all pages)');
+    expect(out).not.toContain('undefined/15');
+  });
+});