docs: Fix broken documentation links in llms.txt

[QueryPlanner]

Priority: Low

Level of Effort: Low

Description

Multiple links in llms.txt are broken (returning 404) due to recent documentation reorganizations and file removals in the google/adk-docs repository. This issue tracks updating the outdated references so all links resolve successfully to their new locations.

Verification / Definition of Done (Passing Criteria)

To verify this issue is resolved without relying on manual user interaction:

1. A python-based validation script must extract all URLs from llms.txt and verify that each URL returns an HTTP 200 status code.
2. The verification script must run automatically and exit with code 0 on success, or code 1 if any URL is broken or returns an error.
3. Running python3 -c "import re, urllib.request; ..." (as outlined in the reproduction) must return no failures.

Sources

• Current llms.txt file: llms.txt in the main branch of google/adk-python
• Official Documentation repository: https://github.com/google/adk-docs
• Detailed mapping of broken paths to their updated counterparts:

Old Link	Correct New Link
https://github.com/google/adk-docs/blob/main/docs/agents/models.md	https://github.com/google/adk-docs/blob/main/docs/agents/models/index.md
https://github.com/google/adk-docs/blob/main/docs/agents/multi-agents.md	https://github.com/google/adk-docs/blob/main/docs/workflows/index.md
https://github.com/google/adk-docs/blob/main/docs/community.md	https://github.com/google/adk-docs/blob/main/docs/community/index.md
https://github.com/google/adk-docs/blob/main/docs/contributing-guide.md	https://github.com/google/adk-docs/blob/main/docs/community/contributing-guide.md
https://github.com/google/adk-docs/blob/main/docs/deploy/agent-engine.md	https://github.com/google/adk-docs/blob/main/docs/deploy/agent-runtime/index.md
https://github.com/google/adk-docs/blob/main/docs/get-started/quickstart.md	https://github.com/google/adk-docs/blob/main/docs/get-started/python.md
https://github.com/google/adk-docs/blob/main/docs/get-started/testing.md	https://github.com/google/adk-docs/blob/main/docs/evaluate/index.md
https://github.com/google/adk-docs/blob/main/docs/observability/arize-ax.md	https://github.com/google/adk-docs/blob/main/docs/integrations/arize-ax.md
https://github.com/google/adk-docs/blob/main/docs/observability/phoenix.md	https://github.com/google/adk-docs/blob/main/docs/integrations/phoenix.md
https://github.com/google/adk-docs/blob/main/docs/sessions/session.md	https://github.com/google/adk-docs/blob/main/docs/sessions/session/index.md
https://github.com/google/adk-docs/blob/main/docs/streaming/custom-streaming-ws.md	https://github.com/google/adk-docs/blob/main/docs/streaming/index.md
https://github.com/google/adk-docs/blob/main/docs/streaming/custom-streaming.md	https://github.com/google/adk-docs/blob/main/docs/streaming/index.md
https://github.com/google/adk-docs/blob/main/docs/tools/authentication.md	https://github.com/google/adk-docs/blob/main/docs/tools-custom/authentication.md
https://github.com/google/adk-docs/blob/main/docs/tools/built-in-tools.md	https://github.com/google/adk-docs/blob/main/docs/integrations/index.md
https://github.com/google/adk-docs/blob/main/docs/tools/function-tools.md	https://github.com/google/adk-docs/blob/main/docs/tools-custom/function-tools.md
https://github.com/google/adk-docs/blob/main/docs/tools/google-cloud-tools.md	https://github.com/google/adk-docs/blob/main/docs/integrations/index.md
https://github.com/google/adk-docs/blob/main/docs/tools/index.md	https://github.com/google/adk-docs/blob/main/docs/tools-custom/index.md
https://github.com/google/adk-docs/blob/main/docs/tools/mcp-tools.md	https://github.com/google/adk-docs/blob/main/docs/tools-custom/mcp-tools.md
https://github.com/google/adk-docs/blob/main/docs/tools/openapi-tools.md	https://github.com/google/adk-docs/blob/main/docs/tools-custom/openapi-tools.md
https://github.com/google/adk-docs/blob/main/docs/tools/third-party-tools.md	https://github.com/google/adk-docs/blob/main/docs/integrations/index.md