Add App Intents shortcuts

[RCGV1]

Contributor checklist

Administrative:

• I have read the README.
• I have read the CONTRIBUTING document and understand the caveats in the Pull Requests section.
• I have signed the Contributor Licence Agreement.

Commits and testing:

• My commits are rebased on the latest main branch.
• My commits are well-structured for review.
• My change has been thoroughly tested, and I am not aware of any regressions to existing features or behaviors. Focused unit and device validation are recorded below; the full Signal test suite was not run.
• I have tested my contribution on these devices:
  • iPhone 15 Pro, iOS 26.6.1: installed development build; manually verified headless Quick Send.
  • iPhone 16 Pro simulator, iOS 18.6: focused App Intents test.

Description

Summary

• Add App Shortcuts for Quick Send, Open Chat, New Message, Camera, and Settings.
• Keep Quick Send headless after local device authentication, while foreground shortcuts open Signal.
• Register shortcut parameters at launch so the system refreshes the available shortcuts.

Security and behavior

• Require local-device authentication for every intent.
• Do not expose conversation suggestions or search results while protected data is unavailable or Signal Screen Lock is locked.
• Revalidate a saved recipient before sending, then enqueue the message through Signal's existing sender queue.
• Start Signal's existing background message fetcher for Quick Send so the chat connection is available during headless execution.
• Allow up to 25 seconds for a cold Signal launch before Quick Send reports that Signal is unavailable.

Validation

• swiftformat --lint Signal/AppIntents/SignalAppIntents.swift Signal/test/AppIntentsTest.swift
• git diff --check
• xcodebuild test -workspace Signal.xcworkspace -scheme Signal -configuration Debug -destination 'platform=iOS Simulator,id=1C12F7AC-636D-4BE1-B075-0479A603EB02' -derivedDataPath /tmp/signal-appintents-pr-derived CODE_SIGNING_ALLOWED=NO -only-testing:SignalTests/AppIntentsTest/testOnlyQuickSendRunsWithoutForegroundingSignal -resultBundlePath /tmp/signal-appintents-checklist-2.xcresult -quiet — passed (1 test)
• Built, installed, and launched the development build on an iPhone. Manually verified Quick Send completes without first opening Signal.
• Shortcut gallery screenshot

[RCGV1]

Shortcut gallery

Manual device verification: Quick Send completes without first opening Signal.