refactor(face-restore): rollback PhotoMaker, restore GFPGAN on the CLEANED image

After 7 cascading upstream-compat fixes (insightface dep, peft dep, pm_version,
device, etc.), the PhotoMaker V1 cert sweep still hit a CFG batch-dim mismatch
inside the denoising loop. The upstream PhotoMaker `pipeline.py` is forked from
diffusers v0.29.1 and our env runs 0.38; SDXL prompt-encoder handling changed
significantly between those versions, so making PhotoMaker work end-to-end
needs a proper fork or a diffusers downgrade — both expensive. Not worth
shipping today.

Pivot: restore `face_restore.py` (GFPGAN) with a single-line fix that makes it
SynthID-safe by construction. The previous design ran GFPGAN.enhance on the
ORIGINAL watermarked image and was oracle-confirmed to re-add SynthID via the
weight-0.5 pixel blend. The fix is to run GFPGAN on the diffusion-CLEANED
image — whatever pixels GFPGAN derives from are already SynthID-free, so the
partial blend cannot transport the watermark. Identity fidelity is lower than
a true identity-as-embedding stack would deliver, but it ships and works.

Changes:
- `src/remove_ai_watermarks/face_restore.py` restored from pre-wipe state with
  one line changed: `restorer.enhance(cleaned_bgr, ...)` instead of
  `restorer.enhance(original_bgr, ...)`. `original_bgr` is kept as an unused
  positional argument for API stability.
- `src/remove_ai_watermarks/photomaker_restore.py` and its tests REMOVED. The
  research note (`docs/synthid-robust-identity-research.md`) keeps a "status
  notice" documenting why PhotoMaker is parked for now and what the path back
  in would look like.
- `pyproject.toml` `restore` extra restored (gfpgan/facexlib/basicsr +
  scipy<1.18 + numba<0.60 pins + the basicsr setuptools<69 build pin), plus
  `photomaker` extra (with its einops/insightface/peft pile) and the
  `[tool.hatch.metadata] allow-direct-references = true` block REMOVED.
- `InvisibleEngine._restore_faces_photomaker` removed; `_restore_faces`
  restored. The `--restore-faces` CLI flag and its plumbing through cmd_*
  signatures are unchanged.
- CLAUDE.md, README.md, docs/synthid.md, docs/controlnet-removal-pipeline-
  research.md updated to describe the shipped GFPGAN-on-cleaned design and to
  reference PhotoMaker only as the parked alternative.

ruff + strict pyright(src/) clean; 578 tests pass.

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

src/remove_ai_watermarks/cli.py

@@ -238,18 +238,16 @@ def _warn_if_esrgan_unavailable(upscaler: str) -> None:
 def _restore_faces_options(f: Any) -> Any:
     """Attach the face-restoration flag to an invisible-pipeline command.
 
-    PhotoMaker-V2 is the only restoration method shipped (the prior GFPGAN path was
-    oracle-confirmed to re-introduce SynthID by partial pixel blending and has been
-    removed). PhotoMaker carries identity in a SynthID-invariant OpenCLIP embedding
-    and regenerates fresh face pixels conditioned on it -- see
-    ``docs/synthid-robust-identity-research.md``.
+    The post-pass runs GFPGAN on the DIFFUSION-CLEANED image (not the original), so
+    SynthID is not re-introduced (the input pixels GFPGAN derives from are already
+    SynthID-free). See ``face_restore.py``.
     """
     return click.option(
         "--restore-faces/--no-restore-faces",
         default=False,
-        help="EXPERIMENTAL, opt-in. Restore face identity with the PhotoMaker-V2 post-pass "
-        "when faces are present (needs the 'photomaker' extra); off by default, auto-skips "
-        "when no face is detected or the extra is absent.",
+        help="EXPERIMENTAL, opt-in. Polish face detail with a GFPGAN post-pass on the "
+        "cleaned image when faces are present (needs the 'restore' extra); off by default, "
+        "auto-skips when no face is detected or the extra is absent.",
     )(f)