fix(lanes): keep stage detection honest across rollbacks and feature switches

Three defects let a lane's pipeline map claim progress that was not this
pass's work, all of them on the "going back" path a new request takes:

- `setStage` cleared the detection columns on a real transition but never
  pruned the `stages` records AHEAD of the new stage. A lane that ran through
  `done` and was then declared back at `plan` rendered `plan` as `current`
  while `tests`/`review`/`done` still read `done`, carrying the previous
  pass's evidence, and contradicting `progress` (computed from the declared
  index alone). A backwards declaration now drops every record it can prove
  is ahead; a key matching no node is unplaceable and left alone.
- `activateFeature` rewrote the live lane row for the incoming feature but
  carried the outgoing one's `detected_*` across. A never-seen slug starts at
  `stage='idle'`/`stages={}`, exactly the shape `inferredDisplayStage` renders
  from detection, so the new feature opened painted with the old one's
  progress — and forward-only rejected every real detection for it until the
  carried-over one aged past DETECTION_TTL_MS. Now cleared, like every other
  real transition; deliberately not archived, since detection is live-only.
- `codex-ingest` classified a rollout journal by raw `now - mtime`, which goes
  negative for a future mtime (clock stepped back, NTP correction, a restore
  that preserved timestamps) and read as "written milliseconds ago". A
  finished thread's journal could replay as live work; a file claiming to be
  from the future is now idle.

Also fixes `check-headers.sh`, which audited via `find` and so reported local
gitignored runtime state (a lane's own `.ccam/profile/hooks/*.sh`) that is not
this repo's source and can never be made compliant here. It now lists files
through git (tracked + untracked-but-not-ignored), so a file an agent just
wrote is still caught before it is staged while ignored state is not.

Tests: 1359 pass (4 new). Header audit exits 0.

skills/file-headers/SKILL.md

@@ -24,8 +24,9 @@ that is missing the header, add it as part of the same change.
 | -------- | -------- |
 | `*.js`, `*.ts`, `*.tsx`, `*.cjs`, `*.mjs` | anything under `node_modules/`, `dist/`, `build/`, `data/` |
 | `*.py`, `*.sh` | vendored/minified files (`*.min.js`) |
-| `*.css` | generated files (they carry their own AUTO-GENERATED banner) |
+| `*.css` | generated files (they carry their own AUTO-GENERATED banner), including the committed `mcp/build/` |
 | | snapshots (`__snapshots__/`), lockfiles, JSON/YAML/Markdown |
+| | anything **gitignored** — local runtime state that happens to live in the checkout (a lane's own `.ccam/profile/hooks/*.sh`, a scratch venv) is not this repo's source and can never be made compliant here |
 
 ## Header formats by file type
 
@@ -106,6 +107,11 @@ bash skills/file-headers/scripts/check-headers.sh
 Exit code `0` = fully compliant; `1` = the printed files are missing headers.
 Run it before finishing any change-set that adds files, and during reviews.
 
+It audits the files **git can see** — tracked plus untracked-but-not-ignored —
+so a file you just wrote is caught before it is staged, while gitignored local
+runtime state is not reported. It therefore needs to run inside a git work tree
+and exits `1` with a message if it is not.
+
 On every pull request, GitHub Actions runs
 `skills/file-headers/scripts/check-headers-pr.sh` against only the
 files changed in the PR diff (added, copied, renamed, or modified). Test locally