Add MkDocs Material documentation site with 40 pages and auto-generated API reference

Sets up a complete documentation website with 7 navigable sections (Home, Getting
Started, User Guide, Architecture, API Reference, Deployment, Development), light/dark
mode, search, code copy, and Mermaid diagram support. API reference pages use
mkdocstrings to auto-generate docs from source docstrings. GitHub Actions workflow
deploys to GitHub Pages on push to main.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/api/tools.md

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+# Tools Module
+
+The tools module implements the tool system used by agents for executing
+actions such as calculations, memory search, file reading, and sub-model
+queries. Each tool implements the `BaseTool` ABC and is registered via
+`@ToolRegistry.register("name")`. The `ToolExecutor` dispatches tool calls
+with JSON argument parsing, latency tracking, and event bus integration.
+
+## Abstract Base Class
+
+### BaseTool
+
+::: openjarvis.tools._stubs.BaseTool
+    options:
+      show_source: true
+      members_order: source
+
+### ToolSpec
+
+::: openjarvis.tools._stubs.ToolSpec
+    options:
+      show_source: true
+      members_order: source
+
+### ToolExecutor
+
+::: openjarvis.tools._stubs.ToolExecutor
+    options:
+      show_source: true
+      members_order: source
+
+---
+
+## Built-in Tools
+
+### CalculatorTool
+
+::: openjarvis.tools.calculator.CalculatorTool
+    options:
+      show_source: true
+      members_order: source
+
+### safe_eval
+
+::: openjarvis.tools.calculator.safe_eval
+    options:
+      show_source: true
+
+### ThinkTool
+
+::: openjarvis.tools.think.ThinkTool
+    options:
+      show_source: true
+      members_order: source
+
+### RetrievalTool
+
+::: openjarvis.tools.retrieval.RetrievalTool
+    options:
+      show_source: true
+      members_order: source
+
+### LLMTool
+
+::: openjarvis.tools.llm_tool.LLMTool
+    options:
+      show_source: true
+      members_order: source
+
+### FileReadTool
+
+::: openjarvis.tools.file_read.FileReadTool
+    options:
+      show_source: true
+      members_order: source