fix: add widget target, push entitlement, error handling, force-unwrap

Phase 1 — Widget extension target:
- Add TabataGoWidget target to project.yml (app-extension, iOS 26.0)
- Embed in TabataGo, add to scheme build targets

Phase 2 — Push notification capability:
- Add aps-environment: development to TabataGo.entitlements
- Required by iOS 26 for AppIntents-based Live Activity buttons

Phase 3 — Error handling hardening:
- Catch ActivityAuthorizationError specifically with user message
- Truncate generic errors to 200 chars to avoid UI overflow
- Fix force-unwrap at WorkoutLiveActivity.swift:556 (widgetURL)

tabatago-swift/TabataGo/Resources/TabataGo.entitlements

@@ -8,6 +8,8 @@
 	<array>
 		<string>health-records</string>
 	</array>
+	<key>aps-environment</key>
+	<string>development</string>
 	<key>com.apple.security.application-groups</key>
 	<array/>
 </dict>

tabatago-swift/TabataGo/ViewModels/PlayerViewModel.swift

@@ -455,8 +455,12 @@ final class PlayerViewModel: ObservableObject {
             )
             liveActivityError = nil
             observeActivityState()
+        } catch let authError as ActivityAuthorizationError {
+            liveActivityError = "Live Activities: \(authError.localizedDescription)"
         } catch {
-            liveActivityError = error.localizedDescription
+            let msg = error.localizedDescription
+            let truncated = msg.count > 200 ? String(msg.prefix(200)) + "…" : msg
+            liveActivityError = "Live Activity error: \(truncated)"
             print("❌ Failed to start Live Activity: \(error.localizedDescription)")
         }
     }