Keep chat streams alive across navigation

[mcintyre94]

Summary

• Fix .reconnecting → .streaming transition: processServiceStream only upgraded status from .connecting to .streaming, so a reconnect that was actively receiving data stayed stuck showing "reconnecting" the whole time. Now also transitions from .reconnecting.

• Skip polling loop when service already stopped: reconnectIfNeeded was fetching service status but discarding the result. Now passes it as serviceAlreadyStopped to reconnectToServiceLogs, which exits after one log fetch instead of making a redundant status API call and re-entering the loop.

• App-wide ChatSessionManager: Previously ChatViewModel was recreated on every chat switch, cancelling the active stream and requiring a reconnect on return. ChatSessionManager is a @MainActor @Observable cache keyed by chat UUID, injected into the SwiftUI environment at the app root. VMs (and their streams) now survive switching chats or navigating between sprites — connections are only torn down on explicit actions (interrupt, clearing all chats).

Test plan

• Send a message to Claude, switch to another chat mid-response, switch back — should show the response streaming without a reconnect
• Send a message to Claude, navigate to a different sprite, navigate back — stream should still be live
• Background the app while Claude is running, return — should reconnect all cached VMs
• Switch to a chat where Claude already finished while you were away — should catch up on missed events in a single log fetch without entering the polling loop
• Verify status shows .streaming (not .reconnecting) once data is flowing during a reconnect
• Delete all chats via "Start Fresh" — should cleanly detach all cached VMs first

🤖 Generated with Claude Code

[claude]

Bug: remove(chatId:) is never called when individual chats are deleted. ChatSessionManager.remove(chatId:modelContext:) is defined to detach a VM and evict it from the cache, but no call site invokes it. Individual chat deletion goes through chatListViewModel.deleteChat() in SpriteNavigationPanel and ChatSwitcherSheet, but neither was updated to call chatSessionManager.remove(). Result: when a user deletes a chat, ChatViewModel stays in cache with WebSocket stream active, leaking a live network connection. Fix: call chatSessionManager.remove alongside deleteChat in both locations. Also missing: unit tests for ChatSessionManager and tests for .reconnecting to .streaming status transitions as required by CLAUDE.md.