Checkpoint runtime-committed session projections

[lukacf]

Summary

• add a post-machine-commit CoreExecutor hook for committed session snapshots
• have the mob runtime executor save runtime-committed snapshots back to the SessionStore projection
• add runtime ordering/failure tests and a persistent-service projection regression test

Why

0.6.18 made StoreCheckpointer save-capable for runtime-backed sessions, but the MeerkatMachine-owned runtime loop committed turns through RuntimeStore without invoking the SessionStore projection save path. This wires the projection update after the machine commit succeeds, avoiding a pre-commit split-brain while restoring per-turn SessionStore saves for MobKit/UnifiedRuntime consumers.

Tests

• ./scripts/repo-cargo fmt --check
• ./scripts/repo-cargo test -p meerkat-runtime runtime_loop_checkpoint -- --nocapture
• ./scripts/repo-cargo test -p meerkat-session --features session-store checkpoint_updates_session_store_projection -- --nocapture
• ./scripts/repo-cargo test -p meerkat-session --features session-store store_checkpointer -- --nocapture
• ./scripts/repo-cargo test -p meerkat-mob checkpoint_committed -- --nocapture
• git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Wire checkpoint hook for non-mob executors

When runtime-backed sessions run through the existing REST/MCP/CLI/RPC executors, those executors return CoreApplyOutput from PersistentSessionService::apply_runtime_turn but do not override this new hook, so the runtime loop calls this default Ok(()) after the machine commit and the SessionStore projection is never updated. I checked meerkat-rest/src/lib.rs, meerkat-mcp-server/src/runtime_ingress.rs, meerkat/src/surface/runtime_backed.rs, and meerkat-rpc/src/session_executor.rs; only MobSessionRuntimeExecutor delegates to checkpoint_committed_runtime_session_snapshot, leaving those production surfaces with stale persisted projections after each committed turn.

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