Bug: detectPR fails when agent renames branch after spawn

[sigvardt]

Description

When an agent is spawned via ao spawn, ao creates a worktree with a branch name like feat/issue-2 and stores it in session metadata. However, coding agents (Codex, Claude Code) often rename the branch before pushing (e.g. feat/2, feat/1-followup-after-acceptance).

The detectPR method in scm-github searches by --head session.branch, which uses the original branch name from metadata. Since the PR was opened on the renamed branch, the lookup returns nothing. This means:

1. Session status never transitions from working to pr_open
2. No webhook notifications fire for PR events
3. CI status, review state, and merge detection all break

Reproduction

1. ao spawn project 2 (creates branch feat/issue-2)
2. Agent renames branch to feat/2 and pushes
3. Agent opens PR from feat/2
4. ao status shows PR=--, CI=--, status=working indefinitely
5. No webhook events fire

Suggested Fix

Option A (recommended): On each lifecycle poll, re-detect the actual branch from the git worktree (git -C <worktree> branch --show-current) and update session metadata if it changed.

Option B: Lock the branch name so agents can't rename it (less robust, agents may still force-push to new branches).

Impact

All webhook-driven automation (notifications, CI self-healing, review routing) is silently broken when agents rename branches. This is the default behavior for Codex agents.

Workaround

Manually patch session metadata files in ~/.agent-orchestrator/*/sessions/ to match actual branch names.