TinyClaw: add cron orchestration tool after session/spawn baseline

[AlexMikhalev]

Summary

Follow-up for Step 5 parity sequencing: add TinyClaw cron orchestration after landing session tools and spawn baseline.

This issue is intentionally sequenced after:

• TinyClaw: Add session tools and orchestration runway (extend #560) #591 (session tools + orchestration runway)
• TinyClaw: Add agent spawning tool via terraphim_spawner #560 (agent_spawn baseline via terraphim_spawner)

Scope

• Add cron tool surface in crates/terraphim_tinyclaw for scheduled workflows.
• Keep implementation extension-first: reuse existing Terraphim crates/patterns and avoid duplicating OpenClaw internals.
• Start with minimal safe actions (list/status/add/remove or equivalent) with strict input validation.
• Ensure cron runs are isolated and do not regress current session handling.

Acceptance Criteria

• cron tool is registered and callable in TinyClaw.
• Scheduling and dispatch behavior has integration tests.
• Documentation updated for configuration and operational constraints.
• Links back to TinyClaw: Add session tools and orchestration runway (extend #560) #591 and TinyClaw: Add agent spawning tool via terraphim_spawner #560 maintained (no duplicate spawn implementation).

References

• docs/plans/tinyclaw-openclaw-parity-design-2026-02-27.md (Step 5)

[AlexMikhalev]

Implemented in commit c422286: added TinyClaw cron tool (status/list/add/remove), scheduler persistence, runtime wiring, and integration tests.