Verify every doc claim against the source and fix what drifted

Every code-referencing claim in the docs, the README and the rules files was
checked against src/, and each finding was re-derived independently before it
was applied. 35 held, 5 were false positives.

Two of them were code, not text. `InvisibleOptions` promises in its docstring to
mirror `InvisibleEngine`, and two defaults had silently stopped:
`max_resolution=None` reached `_target_size`'s `max_resolution > 0` and raised
`TypeError` on every library call that left the options alone, and
`cpu_offload=True` made a library run slower than the identical CLI run. Both are
fixed, and `TestInvisibleOptionsMirrorTheEngine` compares the two signatures
field by field rather than pinning the two values that happen to be known. A
companion assertion in `TestTargetSize` reads the engine's own declared default,
so a drift on the engine side -- which the mirror check alone would accept,
because both sides would still agree -- fails too.

The user-facing docs: README called `invisible` GPU-optional where it raises
without CUDA, and gave the image `metadata` command `video metadata`'s output
rule, promising the source survives a command that overwrites it. Yuanbao was
missing from the supported-mark list. `veo` was listed among the video policies
that require a run anchor, though its row sets no `anchor_iou`.
`known-limitations` called ControlNet the default profile and contradicted
itself ninety lines below. An unescaped pipe truncated the `hailuo` table row.
The `dev` extra, the CI shape, ffmpeg's role, the sdist boundary and the
strength-curve range were corrected, and `remove_all`/`remove_batch`, the pill
gate, `erase --keep-metadata` and `all`'s CUDA failure mode were documented.

Research notes that described removed modules, extras and flags in the present
tense now say so once in the page banner instead of sentence by sentence, which
covers the whole page rather than the lines that happened to be noticed, and one
fixture is referred to by role rather than by name.

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

docs/installation.md

@@ -48,7 +48,10 @@ uv tool install --force "remove-ai-watermarks[visible,heif]"
 
 ## Video processing
 
-Video metadata inspection and stripping work with the default package. Stable
+Video metadata inspection works with the default package, and MP4 and MOV
+stripping uses the in-tree ISOBMFF box walker. Stripping the non-ISOBMFF
+containers (MKV, WebM, AVI, FLV, and the audio formats) and writing any cleaned
+video need ffmpeg on PATH, for example `brew install ffmpeg`. Stable
 visible-mark identification and removal, full video cleaning, and visible/all
 batch modes need the `video` extra:
 
@@ -102,7 +105,7 @@ application actually uses:
 | `lama` | big-LaMa ONNX fill backend | `visible`, ONNX Runtime | Model download, no Torch |
 | `qwen-zimage` | Invisible image-watermark removal, both CUDA-only profiles | `diffusion`, DiffSynth | Yes |
 | `all` | Every production feature | All rows above | Yes |
-| `dev` | Tests, linting, typing, and upstream parity checks | `visible`, `detect`, upstream invisible-watermark | Yes, for parity tests |
+| `dev` | Tests, linting, typing, and upstream parity checks | `video`, `detect`, upstream invisible-watermark | Yes, for parity tests |
 
 Dependency composition:
 
@@ -188,8 +191,10 @@ Run the complete project gate:
 bash maintain.sh
 ```
 
-The script runs dependency checks, linting, formatting checks, type checking,
-and the test suite.
+The script syncs every optional backend on top of the `dev` environment above,
+then runs dependency checks, linting, formatting, type checking, and the test
+suite. It applies Ruff fixes and formatting in place rather than only reporting
+them.
 
 ## Hugging Face authentication