Collapse the duplicated detection path and lift the image pipeline into the library

The visible-mark path had grown three copies of one ladder sweep, four
near-identical `detect` arms, and four hand-rolled `footprint_mask` overrides;
mark knowledge sat in five hand-maintained tables across three modules; and the
flagship `all`/`batch` pipeline existed only in cli.py, written twice with
divergent behavior.

Detection is now one measurement. `_ladder_best` replaces the three sweeps,
`_scan`/`_verdict` replace the four arms, and the winning box travels to the
mask on `TextMarkDetection.match_box` instead of being swept a second time.
`detect_both` returns the strict and relaxed verdicts from one scan, which
halves the arbiter's perception cost (260 -> 130 matchTemplate calls on a 2048²
image, verdicts identical field for field). A per-mark demotion goes in the new
`_post_gate` hook, never in a `detect` override -- an override is invisible to
the single-pass path, which is how the RunningHub and Yuanbao anchor gates
briefly stopped applying.

Everything about a mark is now one registry row: product, label regime, the
platform sentence `identify` reports, the metadata signals that confirm it, and
its TC260 producer codes. `identify._VISIBLE_MARK_PLATFORM`, the signal mapping
in `api.visible_provenance`, `_PRODUCT_OF` and the pill veto are derived from
those rows.

`api.remove_all` / `api.remove_batch` are the library form of the `all` and
`batch` commands; the CLI is a wrapper that owns console text and exit codes.
Progress is a `(stage, detail)` pair of stable tokens, so the CLI keys its
wording off structure rather than parsing the library's prose back.

Two intentional behavior changes, both verified against a recorded 811-image
sample of detector verdicts, removal-mask hashes, arbiter decisions and
`identify` reports:

  * A TC260 label now relaxes the vendor its `ContentProducer` names rather than
    ByteDance's pair on every China-AIGC image. 333 of 811 samples move; on 185
    of them the previously relaxed pair was simply the wrong vendor, and the
    mark actually present never reached the relaxed gate its own
    `provenance_ncc_factor` was calibrated for.
  * A confident LibLibAI detection suppresses the Jimeng pill, like every other
    TC260 product's mark. It was registered alongside RunningHub and Baidu, both
    of which were added to the hand-written veto list, and it was not. 1 sample
    moves, and it is exactly the co-firing case.

Nothing else in that record changes: detector verdicts, mask hashes and
`identify` verdicts are byte-identical, and all 200 calibration constants are
untouched.

Also: `aigc_label` and friends plus `extract_c2pa_info` are memoized on
(path, mtime_ns, size) -- size because this package rewrites in place; the
native TC260 container readers route on magic bytes instead of the file
extension, so a mislabeled AVI or FLV is no longer invisible; `identify` shares
one pixel decode between the DWT-DCT and visible stages (TrustMark keeps its own
Pillow decode, which is not substitutable); and the six `stabilize_*` video
wrappers collapse into one policy table.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/ladder_headroom.py

@@ -1,7 +1,7 @@
 """How much recall is the coarse scale ladder costing, and what would a denser one cost?
 
 THE FINDING THIS MEASURES
-  `_tophat_score` sweeps three rungs -- (0.8, 1.0, 1.25) -- and the `binary` front-end
+  `_ladder_best` sweeps three rungs -- (0.8, 1.0, 1.25) -- and the `binary` front-end
   sweeps none at all. Measured on stamped marks over controlled backgrounds
   (`scripts/detector_response.py`), the response is a COMB: doubao scores 0.99 exactly at
   each rung and collapses to 0.37-0.48 between them, against a 0.50 gate. So a mark whose
@@ -93,7 +93,10 @@ def wilson(k: int, n: int, z: float = 1.96) -> tuple[float, float]:
 
 
 def score_at_scales(engine: Any, image: np.ndarray, scales: tuple[float, ...]) -> dict[float, float]:
-    """`_tophat_score`'s inner loop, opened up so the ladder is a parameter.
+    """`_ladder_best`'s inner loop, opened up so the ladder is a parameter.
+
+    A DELIBERATE second copy of the sweep: it exists to measure ladders the shipped
+    engine does not have, so it must not be folded back into `_ladder_best`.
 
     Deliberately reaches into the engine (`tophat_response`, `_glyph_silhouette`): a
     measurement script may, product code may not. Kept a faithful copy of the shipped