fix: bound loaded profile context

[vycdev2]

Summary

• bound persisted user profiles and server memory when loading them into Claude context, preserving the configured 2,000/10,000-code-unit limits for oversized existing files
• stop before a UTF-16 surrogate pair when a legacy file crosses the read boundary
• cover exact ASCII caps and Unicode-safe reads for both storage paths

Verification

• RED on untouched upstream/main: the focused test loaded all 2,500 profile characters instead of 2,000
• npm run build — passed
• node --test tests/profileStorageBounds.test.mjs — passed
• npm test — passed (66 tests)
• direct node-pty import — passed
• git diff --check — passed

Distinctness

• PR fix: preserve profile Unicode boundaries #83 protects new profile and server-memory writes at their Unicode boundaries; this PR independently bounds oversized persisted files when they are read, while preserving the same Unicode invariant.

Risk

• Low: files are not rewritten, shorter values are unchanged, and a cap that falls inside an astral character stops one UTF-16 code unit earlier rather than returning an invalid half-character.

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