Module journal 

Journal / Resume — checkpoint persistence with replay semantics (M1).

Provides:

• JournalStore — wraps RunStore with cache-key index for O(1) lookups
• AgentCacheKey — deterministic blake3-based key for agent invocations
• JournalCallback trait — scheduler integration hook
• ResumeContext — orchestrates run recovery
• gc_runs() — cleanup old completed runs

Thread safety: All public methods take &self (interior mutability via RwLock). The underlying checkpoint data is protected by a single writer lock.

Lifecycle: new() → init_run() → cache_agent()* → flush() 或: open() → has_completed()/get_cached() → workflow resume logic

Structs

AgentCacheKey

Deterministic cache key for an agent invocation. Normalizes whitespace/unicode to ensure cache hits across formatting differences.

CompositeJournalCallback

Composite callback that chains multiple JournalCallback implementations.

JournalStore

JournalStore wraps RunStore with replay semantics.

ResumeContext

Context for resuming a run.

Enums

JournalError

RunCreationMode

Options for creating a run (new or resume).

Functions

gc_runs

Clean up old completed/cancelled runs.