Harden Agent OS installation and adapters

[jarmo-blip]

Summary

• harden profile installation and synchronization with staged writes, manifests, path validation, and local-change protection
• add Claude Code, Codex, Cursor, and Antigravity adapters
• add full-path standards indexing, doctor and manifest-scoped uninstall commands
• make prompts host-agent independent and add context and validation guidance
• add functional regression tests, ShellCheck, and CI

Why

The packaged default profile did not install correctly, shell counters could
terminate scripts under set -e, nested standards collided in the YAML index,
and profile names could escape the intended directory. Installation also only
implemented a Claude-specific destination despite broader compatibility claims.

Impact

Existing unmanaged standards are preserved. Manifest-managed local edits fail
closed unless --force is explicitly supplied. Installations can be previewed
with --dry-run, diagnosed with doctor.sh, and removed using the scoped
manifest-based uninstaller.

Validation

• bash -n scripts/*.sh install_agent_os.sh tests/run.sh
• ./tests/run.sh — 14/14 passed
• ShellCheck — passed with no findings
• YAML parsing for config.yml and .github/workflows/test.yml
• git diff --check
• repo-auditor strict/SARIF diff audit against
  cae8e664fb59a01869718c3151e0f45b7a06a2fb — 19 changed files, 0 scoped findings