Fix UTF-8-safe evolution trigger logging

[cursor]

Summary

• Fix a crash in manual evolution trigger logging when long CJK/emoji summaries are clipped at a non-UTF-8 byte boundary.
• Reuse the existing UTF-8-safe clipping helper and add regression coverage for the boundary case.

Task Linkage

• Task ID: TASK-2026-066
• Task folder: tasks/TASK-2026-066-utf8-evolution-log-truncate/

Injected Specs

• spec/architecture-boundaries.md (if architecture/layering changed)
• spec/security-nonnegotiables.md (if sandbox/security changed)
• spec/testing-policy.md (required for any code change)
• spec/docs-sync.md (if behavior/docs/env/commands changed; reviewed, docs not needed because command semantics did not change)

Validation Evidence

• Commands executed:
  • rustup update stable && rustup default stable
  • cargo fmt --check && cargo test -p skilllite-commands evolution_desktop && python3 scripts/validate_tasks.py
  • cargo test -p skilllite-commands --features agent manual_trigger_summary_clip
  • cargo clippy --all-targets -- -D warnings && cargo clippy -p skilllite-commands --features agent --all-targets -- -D warnings && cargo test
  • python3 scripts/validate_tasks.py
• Key results:
  • Local Rust/Cargo updated from 1.83 to 1.96 because time 0.3.47 requires edition 2024 support.
  • Agent-feature regression run: 2 passed; 0 failed.
  • Task validation: Task validation passed (66 task directories checked).
  • Full clippy/test command exited 0; final workspace test/doc-test output showed all executed tests passing.

Regression Scope

• Areas likely affected:
  • skilllite evolution run --log-manual-trigger audit/log summary clipping.
  • Desktop manual evolution trigger bridge.
• Explicit non-goals:
  • Evolution scheduling, LLM behavior, database schema, pending skill flow.

Docs Sync (EN/ZH)

• Not needed
• Updated EN + ZH docs
• Files:
  • N/A

Review Checklist

• Acceptance criteria in tasks/.../TASK.md satisfied (or explicitly deferred)
• tasks/.../STATUS.md updated with latest progress
• tasks/.../REVIEW.md includes merge readiness decision
• tasks/board.md status is up to date