Introduces the shared platform that per-agent adapters plug into, wired for the
three shipped harnesses (claude-code, codex, opencode):
- adapters/agent/registry: single source of truth for shipped adapters
(Constructors), consumed by the daemon to resolve a session's harness.
- adapters/agent/activitydispatch + 'ao hooks' command: maps an agent's native
hook callbacks onto AO activity states (active/idle/waiting/...).
- claudecode/codex/opencode: emit SessionStart/UserPromptSubmit/Stop activity.
- HTTP + OpenAPI: report session activity state.
- db: single migration widening sessions.harness to all shipped harnesses, so
adding an adapter needs no further migration.
- domain: harness constants + --agent alias for 'ao spawn'.
Adding a new agent is now one adapter package plus a line in Constructors().
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Harshit Singh Bhandari <claudeagain@pkarnal.com>