v0.42.19.0 fix(skillopt): close the last gap in the AI SDK v6 tool-loop fix (write-capture mapper + regression test) (#1809)

* fix(ai/gateway): AI SDK v6 tool loop on non-Anthropic providers (#1782, #1764)

v6's asSchema() rejected the bare { jsonSchema } object and called it as a
function ("schema is not a function"), killing every tool-using agent run on
non-Anthropic providers and skillopt on all providers. Wrap tool inputSchema
with the SDK jsonSchema() helper, and add a pure toModelMessages() boundary
adapter in chat() that converts tool results to the v6 ModelMessage shape
(role:'tool' + typed output:{type:'json'|'error-text',value}, isError dropped,
non-JSON-safe output normalized). toolLoop stays provider-neutral and unchanged.
Both skillopt tool builders (rollout.ts, write-capture.ts) switch to the shared
paramDefToSchema mapper so enum/default/items survive. Tests run the produced
shapes through real generateText + MockLanguageModelV3.

Co-Authored-By: michaeladair44 <michaeladair44@users.noreply.github.com>
Co-Authored-By: justemu <justemu@users.noreply.github.com>
Co-Authored-By: JE4NVRG <JE4NVRG@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: bump version and changelog (v0.42.19.0)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: michaeladair44 <michaeladair44@users.noreply.github.com>
Co-authored-by: justemu <justemu@users.noreply.github.com>
Co-authored-by: JE4NVRG <JE4NVRG@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

VERSION

@@ -1 +1 @@
-0.42.18.0
+0.42.19.0