Detect scanned QR sync codes

[MiSikora]

Task/Issue URL: https://app.asana.com/1/137249556945/project/72649045549333/task/1216422585541213?focus=true
Tech Design URL (if applicable): https://app.asana.com/1/137249556945/project/72649045549333/task/1216509582049467?focus=true
API Proposals URL(s) (if applicable): N/A

Description

Detects and handles QR codes scanned with the camera on the "Scan QR" tab of the simplified Sync With Another Device screen, and adds basic validation of scanned and pasted codes.

• Scanning a sync code starts the sync process with the scanned URL. For now this opens the placeholder Sync With Another Device screen, which displays the URL.
• Scanned codes are debounced for 5 seconds. The camera decodes continuously and emits the same code for every frame it stays in view, so without the debounce a valid code would restart the sync flow.
• Scanning a blank code shows a "Sorry, the scanned code is invalid." snackbar instead of starting the sync process. Blank scans are debounced the same way as valid ones.
• Pasting a blank code with the "Paste Sync Code" button on the "Enter Code" tab shows a "Sorry, the pasted code is invalid." snackbar instead of starting the sync process.

Steps to test this PR

Scan a valid sync code

• Open Sync Dev Settings.
• Tap "Launch Sync Settings V2".
• Tap "Sync With Another Device".
• Complete the device authentication prompt.
• Tap "I’m Ready to Scan" on the "Scan QR" tab.
• Grant the camera permission when prompted.
• Point the camera at a sync QR code from another device.
• Verify the placeholder Sync With Another Device screen opens and displays the scanned sync URL.

Scan an invalid code

• On the "Scan QR" tab, point the camera at a QR code that contains only blank text (for example one generated from a single space).
• Verify a "Sorry, the scanned code is invalid." snackbar is shown.
• Verify the sync process does not start.

Paste an invalid code

• Copy blank text (for example a single space) to the clipboard.
• Open the "Enter Code" tab.
• Tap "Paste Sync Code".
• Verify a "Sorry, the pasted code is invalid." snackbar is shown.

UI changes

N/A

---

Note

Medium Risk
Changes sync pairing entry points (camera scan and paste) in v2 UI; incorrect handling could start sync with bad data or spam launches, though scope is limited to the read-sync-code screen.

Overview
Wires the Scan QR camera tab so decoded barcodes flow through ReadSyncCodeViewModel and launch the existing ExchangeSyncCode flow with the scanned text. Decoding runs while the fragment is resumed (with optional QR-only decoding when restrictScannedBarcodesToQrTypes is enabled) and stops when the lifecycle pauses.

Paste validation is tightened: blank clipboard content shows a snackbar via a new ShowMessage command instead of starting sync. The activity handles that command with a Snackbar.

Adds user-facing strings for invalid scanned/pasted codes (scanned invalid message is in resources; paste path uses it). ExchangeSyncCodeActivity uses the generic sync screen title. ViewModel tests cover scan, paste, and blank paste.

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[MiSikora]

• Clean up sync code before integrating pixels #9386
• Avoid signing out of a device when renaming it #9374
• Handle simplified sync deep linking #9373
• Handle restore on reinstall sync scenario #9368
• Simplified sync UI updates #9363
• Handle v1 exchange sync codes #9362
• Handle sync recovery basic scenario #9356
• Add syncing with another device logic and navigation #9343
• Add generic handling of v1 sync errors #9337
• Add sync with another device UI #9334
• Detect scanned QR sync codes #9333 👈 (View in Graphite)
• Handle sync code pasting #9332
• Refactor simplified sync class names #9329
• Handle sync logic on the displayed QR code page #9328
• Display sync QR code in simplified sync #9321
• Make remove device dialog destructive #9317
• Mitigate sync settings UI race condtions #9316
• develop

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Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[MiSikora]

Merge activity

• Aug 4, 12:40 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Aug 4, 12:41 PM UTC: @MiSikora merged this pull request with Graphite.