New 'dev_intent' detection flags iOS/Swift app development in a conversation

What

• A new internal system message subtype, dev_intent, is sent at most once per kind per conversation when Claude has written, read, or run something iPhone-specific in Swift, so hosts like Desktop can react to it (for example, showing an iOS Simulator tip).
• Detection is heuristic: a new detector watches for Edit/Write-style tool calls touching .swift files or Bash commands matching simctl/xcodebuild-like patterns, plus tool results mentioning iOS SDK strings, and fires the dev_intent message with kind ios_app the first time both a Swift file edit and iOS evidence appear in the transcript. A dev_intent_detect telemetry event is also emitted.
• Headless and SDK sessions were previously excluded from this detection (they only carried a plain readFileCache reference); the turn loop for those sessions now creates a per-host dev-intent tracker and feeds it every message as the conversation progresses, so headless/SDK sessions participate too.

Why This lets hosts surface context-appropriate help, like an iOS Simulator tip, the first time a conversation shows real signs of iOS app development, without requiring the user to ask for it, and now works consistently across interactive, headless, and SDK sessions.