feat(detector): deprecate --fast (now a no-op, full scan always)

Since the jsdom removal the static HTML/CSS analysis is fast (~4ms/file) and
covers every rule, so the regex-only `--fast` path only loses coverage (it
ran ~10 of 41 rules) for no real speed win. It's a foot-gun: a `--fast` scan
can read "clean" because most rules silently don't run.

Deprecate gracefully rather than hard-remove: the flag is still accepted (so
existing CI scripts don't break) but ignored, with a one-line stderr notice,
and the full scan always runs. Dropped from --help and the example. Removed
the `--fast` suggestion from the many-files warning and from critique.md's
scan guidance.

Ships to users via a CLI release (npm) and rides the next skill release in
the bundled detector. Tests updated to assert the deprecation behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

skill/reference/critique.md

@@ -60,12 +60,12 @@ Run the bundled detector and browser visualization evidence. Assessment B is man
 
 CLI scan:
 ```bash
-node {{scripts_path}}/detect.mjs --json [--fast] [target]
+node {{scripts_path}}/detect.mjs --json [target]
 ```
 
 - Pass markup files/directories as `[target]`; do not pass CSS-only files.
 - For URLs, skip CLI scan and use browser visualization.
-- For 200+ scannable files, use `--fast`; for 500+, narrow scope or ask.
+- For very large trees (500+ scannable files), narrow scope or ask.
 - Exit code 0 = clean; 2 = findings.
 - If the detector entrypoint is missing or fails to load, report deterministic scan unavailable and continue with browser/manual review.