fix: deduplicate memory rendering

[davidrobertson]

Summary

• render derived memory titles once in SessionStart, enrichment, and working-context output
• preserve independently authored titles, including short titles that prefix longer content
• cover short and long derivation, surrogate boundaries, XML escaping, and all three renderers

Validation

• npm test - 1,734 passed, 1 skipped
• npm run build
• LazyCodex QA, code review, and final gate passed for 112df273888091bd071ee601935e9338c029eeef