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_platform.py

@@ -20,7 +20,6 @@ from remove_ai_watermarks.noai.watermark_profiles import (
     GEMINI_STRENGTH,
     OPENAI_STRENGTH,
     UNKNOWN_STRENGTH,
-    get_model_id_for_profile,
     normalize_profile,
     resolve_strength,
     strength_default_help,
@@ -111,24 +110,19 @@ class TestMpsErrorDetection:
 
 
 class TestModelProfiles:
-    """Tests for watermark_profiles.py."""
+    """Tests for watermark_profiles.py profile-name normalization."""
 
-    def test_sdxl_profile(self):
-        assert get_model_id_for_profile("sdxl") == "stabilityai/stable-diffusion-xl-base-1.0"
+    def test_canonical_profiles_unchanged(self):
+        assert normalize_profile("sdxl") == "sdxl"
+        assert normalize_profile("controlnet") == "controlnet"
 
     def test_default_alias_resolves_to_sdxl(self):
         # "default" is the legacy alias for "sdxl" (back-compat for existing scripts).
-        assert get_model_id_for_profile("default") == "stabilityai/stable-diffusion-xl-base-1.0"
         assert normalize_profile("default") == "sdxl"
-        assert normalize_profile("controlnet") == "controlnet"
 
-    def test_controlnet_profile(self):
-        # controlnet shares the SDXL base checkpoint (the ControlNet is an add-on).
-        assert get_model_id_for_profile("controlnet") == "stabilityai/stable-diffusion-xl-base-1.0"
-
-    def test_unknown_profile_raises(self):
-        with pytest.raises(ValueError, match="Unknown model profile"):
-            get_model_id_for_profile("nonexistent")
+    def test_normalize_is_case_and_whitespace_insensitive(self):
+        assert normalize_profile("  Default ") == "sdxl"
+        assert normalize_profile("CONTROLNET") == "controlnet"
 
 
 class TestResolveStrength: