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>

docs/synthid.md

@@ -570,7 +570,7 @@ table.
 schedule to `resolve_strength`, do not reuse the default ladder; (2) the
 `--restore-faces` pass is now SynthID-safe by construction (the GFPGAN-on-original
 path that re-added SynthID was removed 2026-06-04; the shipped restore is
-PhotoMaker-V1, identity-as-embedding, see `synthid-robust-identity-research.md`); (3)
+GFPGAN-on-cleaned, see `face_restore.py`); (3)
 removal near threshold is seed-non-deterministic -> FIX the prod seed (kills the
 coin-flip; ship a deterministic certified config).