feat: support caller-supplied session names

[codesoda]

Summary

• add an optional name parameter to the Agent tool
• use it for foreground and background subagent sessions while preserving the short agent-ID suffix
• persist it with scheduled jobs and apply it when those jobs fire
• trim caller input and fall back to the configured agent name/type when it is empty

Motivation

Descriptions are intentionally short task summaries, but callers may need stable, human-readable session labels for persisted subagent runs. A separate name lets orchestrators label sessions without changing the task description shown in the UI.

Testing

• npm run lint
• npm run typecheck
• npm run test (738 passed, 5 skipped)
• npm run build