chore: update action pins and shared project instructions

[ob-aion]

Summary

• Update pinned GitHub Actions dependencies across reusable workflows and self-CI. Includes chore(deps): bump the actions group across 1 directory with 5 updates #40.
• Share project instructions through AGENTS.md and a single CLAUDE.md import. Keep security contracts and release ownership explicit.
• Bump the manual release version to 0.2.11 and update the changelog. The tag workflow moves v0; the GitHub release remains manual.

Test plan

• actionlint -shellcheck=shellcheck, yamllint -c .yamllint ., and secret scan for the action updates.
• Markdown structure, instruction references, and git diff --check.
• Twenty remote checks passed for the dependency update; final-head checks run after this documentation commit.