feat(mesh): add Xquik fallback and repair Mesh docs links

[kriptoburak]

Description

Adds Xquik as an optional provider for TwitterInfoAgent. When the primary
provider is unavailable or unconfigured, XQUIK_API_KEY enables profile
lookup, timelines, search, tweet detail, thread context, and replies before the
agent uses its final fallback.

The integration preserves the existing response shape, sends credentials only
through environment-backed request headers, forwards requested timeline limits,
updates agent metadata, and includes mocked examples that require no live key.

Independent Repository Fix

The API documentation links in both README.md and mesh/README.md redirected
to a 404 page. They now point to the current Heurist Mesh overview, which returns
HTTP 200.

Related Issues / Tickets

None.

How Has This Been Tested?

• uv run --python 3.12 python mesh/tests/twitter_info_agent_xquik.py
• uv run --python 3.12 python -m py_compile mesh/agents/twitter_info_agent.py mesh/tests/twitter_info_agent_xquik.py
• uv run --python 3.12 ruff check --line-length=120 mesh/agents/twitter_info_agent.py mesh/tests/twitter_info_agent_xquik.py
• uv run --python 3.12 ruff format --check --line-length=120 mesh/agents/twitter_info_agent.py mesh/tests/twitter_info_agent_xquik.py
• git diff --check
• Confirmed the parser uses Xquik's default v1 payload keys.
• Added a regression assertion for the exact environment-backed request header.
• Rebased the single signed commit onto the current upstream main.
• Old documentation URL: redirect followed by HTTP 404.
• New documentation URL: redirect followed by HTTP 200.

Checklist

• Documentation: Updated agent metadata, provider table, and broken API documentation links.
• Tests:
  • Added a mocked agent test script with saved YAML output.
  • No tests needed for this PR.
• Metadata: Updated TwitterInfoAgent metadata.
• No Duplicates: Checked repository content and open or closed issues and pull requests.
• No Breaking Changes: Existing providers and tool response shapes remain supported.

Xquik is an independent third-party service. Not affiliated with X Corp.
"Twitter" and "X" are trademarks of X Corp.

[kriptoburak]

Audited and repaired this contribution at signed commit 7980f65503a623981563515e3e80cfc7f6202402.

The Xquik request previously opted into normalized snake_case responses while the provider parsed default v1 camelCase fields. Real responses could therefore lose dates and engagement metrics. The request now sends only the environment-backed API key, matching the parser and fixtures. A focused assertion protects that contract.

The branch is rebased onto current upstream main. The mocked agent run, Python compilation, Ruff lint, Ruff formatting, documentation links, signature, and git diff --check all pass.