docs(community): point governance to caipe-io and drop CNOE branding

[sriaradhyula]

Summary

• Replaces SIG Governance / CNOE Agentic AI SIG references with Governance pointing to caipe-io/governance
• Updates community docs, landing page, footer, README, and calendar invite to use CAIPE community language instead of CNOE/SIG branding
• Renames the community calendar file to caipe-community-meeting.ics (organizer: caipe-community@googlegroups.com)
• Updates SECURITY.md to use caipe-security@googlegroups.com for private security reports
• Points CODE_OF_CONDUCT.md (and MCP copies) at caipe-io/governance with caipe-maintainers@googlegroups.com for conduct reports

Out of scope for now: cnoe-io GitHub/registry URLs, copyright headers, release notes, and workshop/tools-utils narrative references.

Type of Change

• Documentation

Test plan

• Open /community and confirm the Governance card links to https://github.com/caipe-io/governance
• Verify docs community page and README quick links use CAIPE wording and updated governance URL
• Confirm footer Community links no longer reference CNOE Agentic AI SIG governance
• Verify SECURITY.md lists caipe-security@googlegroups.com and CODE_OF_CONDUCT.md lists caipe-maintainers@googlegroups.com

[github-actions]

✅ No proprietary content detected. This PR is clear for review!

[github-actions]

ℹ️ Branch is behind main (advisory, non-blocking)

Commit: ac48ffe6

This branch does not yet contain the latest main. This does not fail the version-bump check — version files are bumped once the branch is updated, and GitHub branch protection still requires the branch to be up to date before merge. Use the Update branch button on this PR, or run:

git fetch origin main
git checkout docs/community-governance-caipe
git merge FETCH_HEAD
git push