Fix critical regression crash and workspace scoping paths

[cursor]

Summary

• Fixes two crash-class UTF-8 byte slicing bugs in LLM embedding unexpected-response previews and task-planner parse failure previews.
• Ensures desktop-triggered background evolution runs pass the selected --workspace, matching the UI status/backlog/authorization DB paths.
• Reuses the existing SKILL_MD_SECURITY_NOTICE for high-risk reference docs and bash-tool docs injected into prompts.

Task Linkage

• Task ID: TASK-2026-069
• Task folder: tasks/TASK-2026-069-critical-regression-fixes/

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)

Additional injected specs:

• spec/verification-integrity.md
• spec/task-artifact-language.md
• spec/rust-conventions.md

Validation Evidence

• Commands executed:
  • rustup update stable && rustup default stable
  • cargo test -p skilllite-agent
  • cargo test -p skilllite
  • python3 scripts/validate_tasks.py
  • cargo fmt --check
  • cargo clippy --all-targets -- -D warnings
  • cargo test
  • sudo apt-get install -y libgtk-3-dev libsoup-3.0-dev libwebkit2gtk-4.1-dev libayatana-appindicator3-dev librsvg2-dev
  • npm ci && npm run build in crates/skilllite-assistant
  • cargo test --manifest-path crates/skilllite-assistant/src-tauri/Cargo.toml
• Key results:
  • Rust/Cargo updated from 1.83.0 to 1.96.0 to support edition 2024 dependencies.
  • cargo test -p skilllite-agent: 249 passed; 0 failed.
  • python3 scripts/validate_tasks.py: Task validation passed (69 task directories checked).
  • cargo clippy --all-targets -- -D warnings: passed.
  • cargo test: passed.
  • Desktop crate test: 50 passed; 0 failed.

Regression Scope

• Areas likely affected:
  • skilllite-agent LLM error handling, task planning, and prompt construction.
  • Desktop bridge background evolution subprocess argument construction.
  • Task workflow artifacts.
• Explicit non-goals:
  • Evolution DB schema changes.
  • Runtime sandbox policy changes.
  • Python SDK changes.

Docs Sync (EN/ZH)

• Not needed
• Updated EN + ZH docs
• Files:
  • N/A; this preserves public CLI/env/docs semantics and applies existing internal safety behavior to missed paths.

Review Checklist

• Acceptance criteria in tasks/TASK-2026-069-critical-regression-fixes/TASK.md satisfied (or explicitly deferred)
• tasks/TASK-2026-069-critical-regression-fixes/STATUS.md updated with latest progress
• tasks/TASK-2026-069-critical-regression-fixes/REVIEW.md includes merge readiness decision
• tasks/board.md status is up to date