fix: address whole-project code review (visible all/batch, engine consolidation, I/O)

Nine findings from a high-effort project-wide review, fixed and verified
(571 passed, ruff/pyright clean):

Correctness:
- all/batch now remove Doubao/Jimeng/Samsung visible text marks: the visible
  step routes through the registry (new cli._remove_visible_auto) instead of a
  hardcoded GeminiEngine, so they no longer leave the wordmark intact.
- batch always reads the original source (dropped the out_path-reuse that
  re-processed already-cleaned outputs on a re-run).
- img2img_runner only retries the diffusion call on the deprecated-callback
  TypeError; any other TypeError now propagates instead of double-running.
- gemini detect/remove and the reverse-alpha engines normalize channels via a
  new image_io.to_bgr, fixing a grayscale/BGRA crash in the FP-gate path.
- _png_late_metadata advances its cursor by the clamped length, so a malformed
  chunk length no longer aborts the late AI-label scan.

Cleanup / efficiency:
- Consolidate the ~90%-identical Doubao/Jimeng/Samsung engines into a shared
  config-driven _text_mark_engine.TextMarkEngine base; each engine is now a thin
  subclass (TextMarkConfig + test shims). Behavior is byte-exact (the three
  engine test suites pass unchanged). Registry adapters collapse to one
  _text_mark(...) row each. Gemini stays a separate engine.
- scan_head is memoized per (path, size, mtime), so identify() reads the file
  head once instead of ~8 times.
- invisible_engine post-processing decodes/encodes the output once (chained in
  memory) instead of 2-4 times across stages.
- Remove the orphaned get_model_id_for_profile (+ CONTROLNET_PROFILE); derive
  the --strength help from the strength constants (strength_default_help) so it
  cannot drift; share the --pipeline/--strength click options; simplify the
  retired --auto resolver.

Net -835 lines. Tests added for the registry-routed visible pass, to_bgr,
the polish/model/guidance wiring, and strength_default_help. CLAUDE.md updated
for the new base module, the engine/registry changes, image_io.to_bgr, and the
scan_head cache.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_cli.py

@@ -374,6 +374,21 @@ class TestAllCommand:
         result = runner.invoke(main, ["all", "/nonexistent/file.png"])
         assert result.exit_code != 0
 
+    def test_all_visible_step_uses_registry(self, runner, sample_png, tmp_path):
+        """Regression (#1): the `all` visible step must route through the registry
+        (best_auto_mark), so Doubao/Jimeng/Samsung text marks are handled -- not just
+        the Gemini sparkle via a hardcoded GeminiEngine."""
+        mock_cls, _mock_engine = _mock_invisible_engine()
+        output = tmp_path / "clean.png"
+        with (
+            patch("remove_ai_watermarks.cli.InvisibleEngine", mock_cls, create=True),
+            patch("remove_ai_watermarks.invisible_engine.InvisibleEngine", mock_cls),
+            patch("remove_ai_watermarks.watermark_registry.best_auto_mark", return_value=None) as mock_best,
+        ):
+            result = runner.invoke(main, ["all", str(sample_png), "-o", str(output)])
+        assert result.exit_code == 0, result.output
+        mock_best.assert_called()  # the registry auto-detector drove the visible pass
+
     def test_all_preserves_rgba_across_invisible_step(self, runner, tmp_path):
         """Regression: ``all`` must keep transparency even when the invisible
         step writes a 3-channel result (as the real diffusion engine does).