fix: bound loaded daily summaries

[vycdev2]

Summary

• Bound each loaded daily summary to HISTORY_RECAP_MAX_CHARS before adding it to Claude's saved channel context.
• Skip empty summaries after trimming.
• Added a regression test covering an oversized stored summary.

Verification

• npm ci — passed; npm reported 13 audit vulnerabilities and a pending node-pty install-script approval warning.
• npm run build — passed.
• node --test tests/summaryContext.test.mjs — RED on untouched main, GREEN after the fix.
• npm test — passed (66 tests).
• node --input-type=module -e "const p=await import('node-pty'); console.log(typeof p.spawn)" — passed (function).
• git diff --check upstream/main...HEAD — passed.

Risk

• Low: only oversized historical summary context is truncated; normal-sized summaries and empty/unset behavior remain unchanged.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.