docs: add framework integration guides for 6 AI agent frameworks (#109)

## Summary

- Add 6 framework integration guides: LangChain, CrewAI, PydanticAI,
LlamaIndex, Mastra, Google ADK
- Redesign docs overview page with Quick Start above fold, compact suite
table, and correct navigation links
- Fix bug: `entryToFixture()` was silently dropping the `endpoint` match
field from JSON fixture files
- Add `endpoint` as discriminator in `validateFixtures()` so
endpoint-only fixtures aren't falsely flagged as catch-alls
- Add fixture examples for each framework under `fixtures/examples/`
- Add "Framework Guides" section to sidebar, README, and overview page

## Test plan

- [x] All 2335 tests pass (including 2 new endpoint tests)
- [x] Commitlint passes (all headers under 100 chars)
- [x] Prettier, ESLint, exports checks pass
- [x] 6-round CR loop converged to 0 findings
- [x] All fixture match keys validated against FixtureFileEntry schema
- [x] All inline doc fixtures verified to match shipped fixture files

Author: jpr5

README.md

@@ -88,9 +88,13 @@ npx aimock convert mockllm ./config.yaml ./fixtures/
 docker run -d -p 4010:4010 -v ./fixtures:/fixtures ghcr.io/copilotkit/aimock -f /fixtures
 ```
 
+## Framework Guides
+
+Test your AI agents with aimock — no API keys, no network calls: [LangChain](https://aimock.copilotkit.dev/integrate-langchain) · [CrewAI](https://aimock.copilotkit.dev/integrate-crewai) · [PydanticAI](https://aimock.copilotkit.dev/integrate-pydanticai) · [LlamaIndex](https://aimock.copilotkit.dev/integrate-llamaindex) · [Mastra](https://aimock.copilotkit.dev/integrate-mastra) · [Google ADK](https://aimock.copilotkit.dev/integrate-adk)
+
 ## Switching from other tools?
 
-Step-by-step migration guides: [MSW](https://aimock.copilotkit.dev/migrate-from-msw) · [VidaiMock](https://aimock.copilotkit.dev/migrate-from-vidaimock) · [mock-llm](https://aimock.copilotkit.dev/migrate-from-mock-llm) · [Python mocks](https://aimock.copilotkit.dev/migrate-from-python-mocks) · [Mokksy](https://aimock.copilotkit.dev/migrate-from-mokksy)
+Step-by-step migration guides: [MSW](https://aimock.copilotkit.dev/migrate-from-msw) · [VidaiMock](https://aimock.copilotkit.dev/migrate-from-vidaimock) · [mock-llm](https://aimock.copilotkit.dev/migrate-from-mock-llm) · [piyook/llm-mock](https://aimock.copilotkit.dev/migrate-from-piyook) · [Python mocks](https://aimock.copilotkit.dev/migrate-from-python-mocks) · [Mokksy](https://aimock.copilotkit.dev/migrate-from-mokksy)
 
 ## Documentation