Provider retry status, session context persistence, and structured usage tracking

[wangtsiao]

Summary

Three feature areas plus supporting fixes, split across 25 commits for clean bisection.

Provider retry status

• Protocol event TurnProviderRetryStatus emitted during exponential backoff between retries
• Provider stream errors (InvalidContentType, network errors) classified as retryable
• CancellationToken-based tool execution cancellation with INTERRUPTED_TOOL_RESULT_MESSAGE
• TUI, CLI JSONL, and Desktop (ACP client + chat UI) display retry status inline
• Interrupted-turn notice relocated to correct prompt position with improved guidance

Session context persistence

• New SessionContextUpdated rollout line records locked session context once per durable file
• append_turn_deduped writes context separately; recorded_session_context survives rollback
• Server lifecycle (agents, goals, research, message edits, interrupts) routes through deduped path

Structured latest-query usage

• SessionMetadata.last_query_usage: Option<TurnUsage> provides structured latest-query tokens
• Replay state tracks latest_query_usage separately from cumulative session totals
• TUI resume/session-switch prefers structured usage over legacy scalar
• Server turn lifecycle (inline, subagent, finalize) populates the field

Misc

• Skip context diff when turn metadata is unchanged
• Desktop ACP compaction handler extracts session id from nested session objects
• TUI blocks user input during session resume with status indicator