feat: handoff staleness detection and workspace-wide handoff listing

[4444J99]

Description

The Active Handoff Protocol (.conductor/active-handoff.md) has no expiration mechanism. A stale handoff file from weeks ago could mislead a new session. There is also no CLI to list all active handoffs across the workspace.

Proposed

1. Add created_at and expires_at fields to handoff files
2. organvm handoff list — show all active handoff files across workspace with age
3. organvm handoff clean [--older-than 7d] — remove expired handoffs
4. Context sync should flag stale handoffs (>48h) in the generated context

Priority

P2 — prevents phantom constraints from misleading agents.

Source

Documentation handoff architecture audit (2026-04-03).

[4444J99]

Backlog engagement 2026-07-19 — disposition: distilled.

Verified delivered on current main: organvm handoff list and organvm handoff clean are wired in src/organvm_engine/cli/__init__.py, implemented by src/organvm_engine/cli/handoff.py, and backed by src/organvm_engine/handoff.py with created_at/expires_at, stale/expired status, age formatting, and cleanup. Tests are present in tests/test_handoff.py.