🐛 fix(session): deliver completion notifications reliably

[zrr1999]

User impact

Session request completions could be persisted without reliably notifying and waking the originating session, especially when channel ingress was disabled or the daemon restarted between completion and delivery.

Root cause

Completion notification was an in-memory follow-up after invocation completion. A process stop, unavailable sender session, or wake projection failure could lose that follow-up even though the source invocation had completed successfully.

Fix

• Persist completion-delivery state atomically with invocation completion.
• Reconcile durable delivery records independently of channel ingress, including after daemon restart.
• Use an atomic claim lease so concurrent reconcilers cannot deliver the same record simultaneously and abandoned claims can be retried.
• Preserve exactly-once mail persistence and sender wake projection across retries.
• Keep the formatter-only session runner change in its own commit before the functional commit.

Validation

• Spark daemon full suite: 64 files, 588 tests passed.
• Spark session suite: 4 files, 44 tests passed.
• Session tool focused suite: 17 tests passed; root focused session/repro total was 30 tests.
• Root typecheck passed with no errors.
• Dependency boundary check passed.
• Full repository format check passed.
• Git diff check passed.