fix: preserve session state on session expiration, abort, and compaction (Fixes #1054)

[Utkarsh-X]

Fixes #1054

Summary

Fixes an issue where sending a message (such as "continue") after a free session expires or after interrupting with Esc causes the assistant to lose all conversation memory and restart exploration from scratch.

Root Cause

1. Missing in-memory state update on errors / session expiration (use-send-message.ts):
   When a free session ends or fails with a gate error, the catch (error) block in use-send-message.ts calls saveChatState to persist the snapshot to disk, but does not update previousRunStateRef.current in React memory. When the user sends a follow-up prompt in the same running session, sendMessage reads the un-synced previousRunStateRef.current, causing sdk/src/run.ts to instantiate a blank initialSessionState (messageHistory = []).

2. Abort race condition (use-send-message.ts):
   When a user interrupts with Esc, the UI input lock was released before client.run() finished resolving without synchronously assigning previousRunStateRef.current = latestRunStateSnapshot.

3. Compaction continuation guidance (compact-history.ts, context-pruner.ts):
   When deterministic compaction runs, the history is collapsed into a synthetic summary. Because the system prompt retains # Initial Git Changes, models seeing 0 assistant turns occasionally re-ran exploratory git diff and tree commands.

Changes

• cli/src/hooks/use-send-message.ts:
  • Assign previousRunStateRef.current = latestRunStateSnapshot and setRunState(latestRunStateSnapshot) inside registerActiveRun upon abort.
  • Assign previousRunStateRef.current = latestRunStateSnapshot and setRunState(latestRunStateSnapshot) in the catch (error) block alongside saveChatState.
• cli/src/hooks/helpers/send-message.ts:
  • Updated the abort listener comment to reflect synchronous state preservation.
• packages/agent-runtime/src/compact-history.ts & agents/context-pruner.ts:
  • Clarified CONTINUATION_TEXT (in 100% parity) to instruct models that initial repository exploration is already recorded in <historical_memory>.

Verification

• bun test sdk/src/__tests__/run-cancellation.test.ts (16 passed)
• bun test cli/src/utils/__tests__/run-state-storage.test.ts (37 passed)
• bun test packages/agent-runtime/src/__tests__/compact-history.test.ts (31 passed)
• packages/agent-runtime/src/__tests__/context-pruner-parity.test.ts (13 passed)
• agents/__tests__/context-pruner.test.ts (69 passed)
• bun run build:sdk and bun run build:freebuff both compile with exit code 0.