feat: add read-only Swagger Petstore agent examples

[sjungwon03]

Summary

Closes #15.

Replace the local-only catalog as the primary integration scenario with a read-only public Swagger Petstore v2 example:

• Add an injected-fetch PetstoreClient fixed to https://petstore.swagger.io/v2, with GET-only requests, timeout handling, response validation, and tolerant filtering of malformed public-demo records.
• Add PetstoreServer with exactly three TypeMCP tools: search_available_pets, get_pet, and get_petstore_inventory.
• Add a deterministic TypeChain workflow that adapts and invokes search_available_pets in-process, then summarizes results without an LLM or MCP transport.
• Add fixture-backed executable tests and separate manual live smoke scripts.
• Document the public-demo volatility and the read-only / no-model-provider / no-hosted-transport boundary.

Verification

• npm ci
• npm run check — 8 test files, 12 tests; production audit reports 0 vulnerabilities.
• npm run example:petstore:typemcp:fixture
• npm run example:petstore:agent:fixture
• npm run example:petstore:live — actual public GET data observed.
• npm run example:petstore:agent — actual TypeChain → TypeMCP-adapted tool result observed.
• git diff --check

Scope and safety

• No POST, PUT, PATCH, or DELETE request path.
• No credential/API-key input or environment configuration.
• CI remains fixture-only; live smoke scripts are manual because Swagger Petstore data is public and mutable.
• This is deterministic tool orchestration, not a model-driven agent, MCP client, or hosted MCP server.

[sjungwon03-ai]

APPROVE at exact head 17af6ce.

All seven review criteria verified against PR diff, CI, and rulesets:

1. Fixed HTTPS host https://petstore.swagger.io/v2 as a const; GET-only via #getJson; no credential field, no configurable base URL, no write method.
2. findAvailablePets validates the whole payload is an array first, then tolerantly filters individual malformed records; throws if zero valid records remain — no silent empty result.
3. PetstoreServer declares exactly search_available_pets, get_pet, get_petstore_inventory with explicit Zod input schemas; test asserts the exact tool name list.
4. summarizeAvailablePets calls createTypeMcpLangChainTools, finds the adapted tool by name, invokes it, and builds a plain deterministic string summary — no LLM, no MCP transport.
5. All unit tests use injected fixture fetch; CI verify.yml runs no :live or :agent command; live scripts are separate manual executables documented as smoke demos.
6. README table, scenario section, and planning doc all match the implemented commands, tool names, and boundaries.
7. No new dependencies; audit:prod in CI; verify check passed at this exact head SHA.

CI: verify completed success at 17af6ce. Ruleset dev active: 1 approval + verify check required. No open review threads.