feat(FN-1118): add mobile sharing and deep-link managers

- Implement ShareManager with native Capacitor sharing, web share fallback, and clipboard fallback plus typed share lifecycle events
- Implement DeepLinkManager with native appUrlOpen and browser hash listeners, URL parsing for fusion schemes and universal links, and error events
- Wire plugin exports and initializePlugins support for share/deepLinks options, and configure Capacitor iOS/Android fusion URL schemes
- Add comprehensive Vitest coverage for sharing and deep-link behavior and document usage in the mobile package README

packages/mobile/README.md

@@ -59,3 +59,103 @@ Use `manager.getDeviceToken()` after registration to retrieve the native device
 This package currently handles **receiving** push notifications and in-app routing events only.
 
 Server-side FCM/APNs delivery infrastructure (token storage, provider credentials, push sending services) is intentionally out of scope for this feature.
+
+## Native Sharing & Deep Links
+
+### ShareManager
+
+`ShareManager` opens platform-native sharing when available and always includes a Fusion deep link in the shared payload.
+
+```ts
+import { ShareManager } from "@fusion/mobile";
+
+const manager = new ShareManager();
+await manager.initialize();
+
+await manager.shareTask({
+  id: "FN-1118",
+  title: "Mobile Plugins - Native Sharing & Deep Links",
+  description: "Implements native share sheet support and deep link parsing.",
+});
+```
+
+#### Share behavior + fallbacks
+
+- Builds a payload with:
+  - `title`: `task.title` or fallback `Task {id}`
+  - `text`: task description (truncated to 200 chars with `...` when needed)
+  - `url`: `${deepLinkBaseUrl}{task.id}` (default base: `fusion://task/`)
+- **Native (Capacitor)**: uses `@capacitor/share`
+- **Web fallback**: uses `navigator.share(...)` when available
+- **Final fallback**: copies the deep-link URL to `navigator.clipboard.writeText(...)`
+
+#### Share events
+
+- `share:success` → `{ taskId }`
+- `share:cancelled` → `{ taskId }`
+- `share:error` → `{ taskId, error }`
+
+### DeepLinkManager
+
+`DeepLinkManager` handles incoming links and emits parsed payloads for app-level navigation.
+
+```ts
+import { DeepLinkManager } from "@fusion/mobile";
+
+const deepLinks = new DeepLinkManager({
+  scheme: "fusion://",
+  universalLinkHosts: ["app.fusion.dev"],
+});
+
+await deepLinks.initialize();
+
+deepLinks.on("deeplink:received", (payload) => {
+  // route to screen/task/project in app UI
+  console.log(payload);
+});
+```
+
+#### Supported URL patterns
+
+- `fusion://task/{taskId}`
+- `fusion://project/{projectId}`
+- `fusion://project/{projectId}/task/{taskId}`
+- `fusion://settings`
+- `fusion://agents`
+- Query params are preserved in `payload.params` for custom-scheme links
+
+Universal links are supported when the host is allowed in `universalLinkHosts`, e.g.:
+
+- `https://app.fusion.dev/?task=FN-123`
+- `https://app.fusion.dev/?project=my-project&task=FN-123&target=task`
+
+#### Deep link events
+
+- `deeplink:received` → parsed `DeepLinkPayload`
+- `deeplink:error` → `{ url, error }`
+
+Use `handleUrl(url)` for programmatic handling (for example, push-notification tap flows that already provide a URL string).
+
+### Integration flow: share -> open -> navigate
+
+A common flow is:
+
+1. Use `ShareManager.shareTask(...)` to share a task link like `fusion://task/FN-123`
+2. Recipient opens that link on mobile
+3. `DeepLinkManager` receives/parses the URL
+4. Your UI listens to `deeplink:received` and navigates to the matching task view
+
+### Capacitor deep-link scheme registration
+
+The Fusion mobile app registers the custom URL scheme in `packages/dashboard/capacitor.config.ts`:
+
+- `server.iosScheme = "fusion"`
+- `server.androidScheme = "fusion"`
+
+### Browser hash listener (development/testing)
+
+On non-native platforms, `DeepLinkManager` listens for hash changes in the form:
+
+- `#deeplink=<encoded-url>`
+
+This hash-based behavior is intended for development/testing only and is not a production universal-link replacement.