docs: add A2A meeting and agenda links

[juanferrub]

Summary

• add a Meetings & Agenda section to the community page
• link the Linux Foundation meetings page for schedule and recordings
• link the public TSC agenda working doc already referenced in GOVERNANCE.md

Closes #1724

Validation

• npx markdownlint docs/community.md --config .github/linters/.markdownlint.json --fix
• attempted full docs build, but the repo docs environment currently fails to resolve a2a-sdk[all] from requirements-docs.txt

[gemini-code-assist]

Code Review

This pull request updates docs/community.md to add a "Meetings & Agenda" section containing links to live community meetings and the TSC meeting agenda working doc. The reviewer suggested using a relative link instead of an absolute GitHub URL for referencing GOVERNANCE.md to ensure better portability across branches and forks.

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[gemini-code-assist]

Since GOVERNANCE.md is located in the root of the repository, it is better to use a relative link instead of an absolute GitHub URL. This ensures the link works correctly across different branches, forks, and when viewing the documentation offline or in alternative environments.

Suggested change

	These links are also referenced in [`GOVERNANCE.md`](https://github.com/a2aproject/A2A/blob/main/GOVERNANCE.md#tsc-meetings).
	These links are also referenced in [GOVERNANCE.md](../GOVERNANCE.md#tsc-meetings).