Say metadata check and strip results are not a clean verdict

docs/cli.md

@@ -157,6 +157,11 @@ remove-ai-watermarks metadata image.png --remove -o clean.png
 When `-o` is omitted, removal overwrites the source. Standard metadata is kept
 unless you pass `--remove-all`.
 
+A quiet `--check` or a successful `--remove` is not a clean verdict. The command
+only inspects and strips embedded AI metadata; a pixel watermark such as SynthID
+has no local decoder once that metadata proxy is gone. `identify` reports the
+same limit.
+
 The command also supports the audio and video containers listed in
 [supported signals](supported-signals.md). ffmpeg must be available for the
 non-ISOBMFF audio and video path.
@@ -225,6 +230,10 @@ remove-ai-watermarks video metadata input.mp4 --check
 remove-ai-watermarks video metadata input.mp4 --remove -o clean.mp4
 ```
 
+As with the generic `metadata` command, a quiet check or a successful strip is
+not a clean verdict: video SynthID is not decoded locally after the metadata
+proxy is gone.
+
 Supported containers are MP4, MOV, M4V, WebM, MKV, AVI, and FLV. The operation
 delegates to the same verified metadata scanner and stripper as the generic
 `metadata` command, so detection and removal stay in parity. Video and audio

docs/module-internals.md

@@ -42,6 +42,10 @@ Important contracts:
 - `invisible` writes no output when no supported local signal is found, unless
   `--force` is supplied.
 - The two no-signal conditions currently share exit code `2`.
+- A quiet `metadata --check` and a successful `metadata --remove` (same for
+  `video metadata`) end by repeating the `identify` limit: the pixel channel is
+  untouched and a watermark such as SynthID has no local decoder once its
+  metadata proxy is gone, so neither outcome is a clean verdict.
 - Hard processing and write failures exit with code `1`.
 - `all` can still write the completed visible and metadata stages when the
   diffusion dependencies are unavailable, but exits with code `1` so the