feat(agent): make task lists durable across context compaction

[su-fen]

Linked issue

Closes #325

Summary

• Replace the full-list TodoWrite protocol with TaskCreate, TaskUpdate, and TaskList using stable executor-assigned task IDs.
• Persist the authoritative runId, revision, and task state in conversation metadata so compaction and prune operations preserve the same task list.
• Atomically flush the finalized history segment before appending a compaction checkpoint, and reject runtime segment switches when persistence fails.
• Clear task state at real user-run boundaries, including edit-resend, while rejecting stale run IDs and degrading corrupt stored task state safely.
• Remove the legacy Todo rendering/sequencing pipeline and keep GUI/Gateway WebUI on the same canonical task-progress projection.

Change scope

• Modules: agent-gui, agent-gui/src-tauri, agent-ui, agent-gateway/web
• Key paths:
  • crates/agent-gui/src/lib/tools/taskState.ts
  • crates/agent-gui/src/lib/tools/taskTools.ts
  • crates/agent-gui/src/lib/chat/compaction/
  • crates/agent-gui/src/lib/chat/history/
  • crates/agent-ui/src/lib/chat/taskProgress.ts
  • crates/agent-ui/src/components/chat/TaskProgressIndicator.tsx

Screenshots / preview

Verification

• pnpm test:gui — 1500/1500 passed
• pnpm test:webui — 539/539 passed
• cargo test --manifest-path crates/agent-gui/src-tauri/Cargo.toml chat_history --lib — 57/57 passed
• pnpm build:gui — passed
• pnpm build:webui — passed
• pnpm lint:gui — passed
• pnpm lint:webui — passed
• cargo check --manifest-path crates/agent-gui/src-tauri/Cargo.toml --tests — passed
• cargo fmt --manifest-path crates/agent-gui/src-tauri/Cargo.toml --check — passed
• pnpm check:ui-boundaries — passed
• git diff --check — passed

Pre-submit checklist

• A requirement issue is linked.
• Synced with the target branch; no merge conflicts at submission time.
• The change is focused on durable task continuity across context compaction.
• No secrets, tokens, or personal data are included.
• Affected behavior and invariants are documented.
• Screenshots / preview added.