check-leftovers: residual edge cases Copilot raised on #463

Loose ends from #463, filed rather than folded in — the PR's gate was green and each of these needs a state that does not occur in practice (rules/boy-scout.md: merge and file, rather than push another commit only to fold them in).

1. The age sentinel is below the accepted floor ceiling

dirt_age_hours starts newest at 999999999 seconds, about 31.7 years. FLOOR_CEILING accepts a floor up to 876,000 hours, about 100 years. A changed path older than the sentinel never updates newest, so the reported age caps at 277,777 hours and a floor above that would read in_progress instead of abandoned.

Fix: track "no age seen yet" as its own state instead of a magic maximum, so every readable mtime participates.

This is the only one of the three with an internal inconsistency rather than a hostile input — the ceiling was added in #463 and the sentinel predates it.

2. Trailing newlines lost in path captures

• self_path="$(git -C "$repo" rev-parse --show-toplevel)"
• the hook's here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

Command substitution strips trailing newlines, so a worktree root or plugin directory whose name ends in one is truncated. Everything downstream then reads a different path. The NUL-safe inventory parsing added in #463 does not cover these two captures.

Fix: a sentinel character around the capture, stripped after.

3. self: null accepted by the hook's envelope guard

A successful detector envelope always carries a self object; null appears only in the exit-2 error envelope, which the hook already rejects before parsing. Accepting null therefore admits a shape the detector never emits on a path that reaches the guard.

Fix: treat null as malformed, and drop the branch that tolerates it.

Not in scope

The bare invocation in skills/release/SKILL.md Step 1 is #465.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HK8Ca6dbz9zLgz4N5xgd6g

Start with the detector's dirt_age_hours logic, then inspect the hook captures for self_path and here and its envelope guard. Check the related guidance in rules/boy-scout.md; done means readable mtimes beyond the old sentinel are handled, trailing-newline paths remain intact, and self: null is rejected.