refactor(web): optimize list lookup paths

[Yevanchen]

Summary

• Optimized thread list actions by indexing allThreads once per list update instead of scanning on each pin/archive/delete action.
• Normalized the Files search query once per view-model build instead of once per file.

Why

• The complexity scan found several list-processing hotspots. These two web list paths are user-facing and safe to improve without changing behavior.

Verification

• Commands:
  • python3 /Users/evanmore/multica_workspaces_desktop-api.multica.ai/baf2a510-889b-4b05-b7c8-c079f5c28938/c87b99f0/codex-home/skills/complexity-optimizer/scripts/analyze_complexity.py /Users/evanmore/multica_workspaces_desktop-api.multica.ai/baf2a510-889b-4b05-b7c8-c079f5c28938/c87b99f0/workdir/mosoo --format markdown
  • just test-file apps/web/tests/files-list-model.test.ts
  • just tc-package @mosoo/web
  • just test-package @mosoo/web
  • just fmt-check-path apps/web/src/routes/files/files-list-model.ts
  • just fmt-check-path apps/web/src/routes/threads/model/use-actions.ts
  • bun run --filter @mosoo/web lint
  • just commit-check
• Manual steps: N/A
• Not run: full just check

Impact

• User/API/contract changes: no API or contract changes; UI behavior preserved.
• Generated files / GraphQL / DB / lockfile: no generated files, GraphQL output, DB migrations, or lockfile changes.
• Env or config changes: none.
• Risk and rollback: low; rollback by reverting this commit.

Review

• Closest review areas: Files list filtering; Threads pin/archive/delete actions.
• Known trade-offs: The thread ID map costs one O(n) rebuild when allThreads changes, then gives O(1) action lookup.