release: promote real TypeChain Petstore agent

[sjungwon03]

Summary

Closes #25.

Promote the reviewed real TypeChain Petstore agent factory from dev to release-only main.

• Exact source: dad97d7fe2ef66d87e1054008d731211cafcada9
• Main is a verified ancestor of current dev after reconciliation PR chore(release): reconcile main history for agent promotion #24.
• Feature implementation was independently approved in PR feat: add real TypeChain Petstore agent factory #22; the two-parent ancestry reconciliation was separately approved in PR chore(release): reconcile main history for agent promotion #24.

Included behavior

• createPetstoreAgent({ model, server? }) delegates real LangChain agent construction to TypeChain createTypeMcpAgent().
• The caller supplies its model; this repository selects no provider, reads no credentials, and adds no provider package.
• The fixture agent loop uses FakeToolCallingModel to select and execute the TypeMCP search_available_pets tool.
• Existing Swagger Petstore client and MCP tools remain fixed-host and read-only.

Required release evidence

• Exact source remains the canonical dev branch.
• verify and release-promotion must pass at the exact source head.
• A fresh independent approval must target that same head.
• Review threads must be resolved before squash merge.

[sjungwon03-ai]

Independent release-promotion review at exact head dad97d7fe2ef66d87e1054008d731211cafcada9 — APPROVE.

• Ancestry: dev head equals PR head; main (a74b30a) is a strict ancestor (compare status ahead, 13/0). Reviewed feature PR #22 and reconciliation PR #24 are both merged and in this head's ancestry.
• Scope: only the reviewed real agent factory, fixture runner, fixture-loop test, README copy, and planning doc. package.json adds one script; no dependency, provider, override, or CI regression.
• Contract: createPetstoreAgent() delegates to createTypeMcpAgent(), injects the explicit Petstore resolver, and leaves model selection/auth to the caller.
• Evidence: FakeToolCallingModel drives an actual LangChain agent loop that selects and executes the read-only search_available_pets tool (asserted via ToolMessage), not direct tool invocation.
• Boundary: no provider credential, process.env, transport, MCP client/session, or write-path claim anywhere in the diff.
• Gates: verify (×2) and release-promotion all green at this exact head; zero unresolved review threads; release label and sjungwon03 assignment present.