feat(camera): share jpeg transcoder + default maxWidth

docs/camera.md

@@ -28,7 +28,7 @@ All camera access is gated behind **user-controlled settings**.
 - `camera.snap`
   - Params:
     - `facing`: `front|back` (default: `front`)
-    - `maxWidth`: number (optional)
+    - `maxWidth`: number (optional; default `1600` on the iOS node)
     - `quality`: `0..1` (optional; default `0.9`)
     - `format`: currently `jpg`
   - Response payload:
@@ -112,6 +112,9 @@ clawdis-mac camera clip --duration-ms 3000      # prints MEDIA:<path>
 clawdis-mac camera clip --no-audio
 ```
 
+Notes:
+- `clawdis-mac camera snap` defaults to `maxWidth=1600` unless overridden.
+
 ## Safety + practical limits
 
 - Camera and microphone access trigger the usual OS permission prompts (and require usage strings in Info.plist).