feat: add flow run title API

[osolmaz]

Summary

• add a flow-level run title API via flow.run.title
• persist runTitle through flow state, manifests, CLI output, and replay-viewer recent-run summaries
• configure pr-triage to emit descriptive titles like PR-triage-acpx-167

Design

The new API is intentionally run-scoped, not flow-name scoped:

• flow.name stays stable for IDs, routing, and file naming
• flow.run.title is resolved once at run start and used only as display metadata
• flows can provide either a static string or a function of { input, flowName, flowPath }

That keeps the title flexible for future workflows without turning flow.name into a user-visible convention bucket.

Validation

• pnpm run check
• real runtime verification using the actual pr-triage flow object with a fast single-node slice

Verified runtime result:

• input: {"repo":"openclaw/acpx","prNumber":167}
• generated title: PR-triage-acpx-167
• persisted in both result.state.runTitle and manifest.json

[osolmaz]

Landed via temp rebase onto main.\n\n- Gate: validation completed for this repo's change scope\n- Land commit: 79715e2\n- Merge commit: e75d471\n\nThanks @osolmaz!