labels: refactor pixelogic + ctrm onto shared platform + hardening

Closes the platform unification: every label parser now routes
purpose/qualifier/codec classification through one source of truth
(vocab.rs) instead of N hand-rolls, and every binary-blob byte
scanner goes through one helper (text::extract_ascii_strings).

pixelogic.rs:
- Drop local extract_strings (~20 lines) — use text::extract_ascii_strings.
- HARDENING: replace  with skip-unknown-component +
  trace log. Pre-refactor behavior: any single uncatalogued token part
  (e.g. a future codec ID, new framework variant) silently dropped the
  entire stream record. New behavior: skip just the unknown part,
  surface what we know about the stream.
- 8 new unit tests cover basic audio/subtitle paths, commentary,
  descriptive, region variant, the new skip-unknown-component
  regression, and the non-audio/non-subtitle early-out.

ctrm.rs:
- Replace  with
  vocab::purpose(&name). Now word-boundary matched — 'Commenter Pro
  Track' no longer false-matches Commentary.
- Replace  with vocab::qualifier(&name).
  Same word-boundary tightening, plus picks up Forced and
  DescriptiveService for free.
- Preserved structural commentary signal via
  as a fallback when name is silent (e.g. 'audio_commentary_1.name=Track 2').
- 6 new unit tests including the 'Commenter' false-positive regression
  and the SDH-only-on-subtitles boundary.

text.rs:
- Drop module-level dead_code allow now that pixelogic uses
  extract_ascii_strings.

Net: all 5 framework parsers now on the unified platform. Future work
(deluxe Phase D, paramount/criterion XML hardening) builds on the
same scaffolding.

Precommit green.

src/labels/text.rs

@@ -9,11 +9,6 @@
 //! more structured parse path (e.g. `class_reader` for .class) should
 //! prefer that — this helper is for genuinely unstructured input.
 
-// Staged for the pixelogic refactor: pixelogic still has its own
-// extract_strings copy; this is the shared replacement waiting for
-// the refactor. dead-code allow comes off when pixelogic switches.
-#![allow(dead_code)]
-
 /// Walk `data`, emit every maximal run of printable-ASCII bytes
 /// (`0x20..=0x7E`) whose length is at least `min_len`.
 ///