feat: add Cap deeplinks and Raycast extension

Author: bcornish1797

apps/desktop/src-tauri/DEEPLINKS.md

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+# Cap Desktop Deeplinks
+
+Cap Desktop registers the `cap-desktop://` URL scheme.
+
+## Recording controls
+
+### Start recording
+
+```bash
+open 'cap-desktop://record/start?mode=studio&capture_type=screen&target=Built-in%20Display&capture_system_audio=true&mic_label=External%20Microphone'
+```
+
+Query params:
+- `mode`: `studio` or `instant` (default: `studio`)
+- `capture_type`: `screen` or `window` (required)
+- `target`: screen/window name exactly as shown in Cap (required)
+- `capture_system_audio`: `true` / `false` (optional)
+- `mic_label`: microphone label exactly as shown in Cap (optional)
+- omitting `mic_label`, `device_id`, `model_id`, and `off` keeps the current Cap inputs unchanged
+- camera:
+  - `device_id=<id>` or `model_id=<VID:PID>`
+  - `off=true` to disable camera
+
+### Stop / pause / resume / toggle / restart
+
+```bash
+open 'cap-desktop://record/stop'
+open 'cap-desktop://record/pause'
+open 'cap-desktop://record/resume'
+open 'cap-desktop://record/toggle-pause'
+open 'cap-desktop://record/restart'
+```
+
+## Device switching
+
+### Switch microphone
+
+```bash
+open 'cap-desktop://device/microphone?label=External%20Microphone'
+```
+
+To disable microphone input:
+
+```bash
+open 'cap-desktop://device/microphone?off=true'
+```
+
+### Switch camera
+
+```bash
+open 'cap-desktop://device/camera?device_id=YOUR_DEVICE_ID'
+open 'cap-desktop://device/camera?model_id=VID:PID'
+open 'cap-desktop://device/camera?off=true'
+```
+
+`off=true` cannot be combined with `device_id` or `model_id`.
+
+## Settings
+
+```bash
+open 'cap-desktop://settings/open?page=hotkeys'
+```
+
+## Backward compatibility
+
+Legacy JSON payload links remain supported:
+
+```bash
+open 'cap-desktop://action?value={...json...}'
+```