fix(app): load workspace sessions by directory

[OpeOginni]

Issue for this PR

Closes #44022

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Stops Settings → Workspaces from freezing the app.

Before: the page fetched every session on the server (serial 100-per-page pagination, no filter) and wrote each one into the store with an unbatched session.remember, so every write re-ran the sorted-sessions memo — O(N² log N) main-thread work that locked the whole UI.

Now: sessions are fetched per workspace directory (the session.list API already supports a directory filter), requests run in parallel, and the store writes are wrapped in Solid's batch() so memos/subscribers update once per fetch. The delete preflight fetches only the target workspace's sessions. Displayed counts still come from the same sessionsForWorkspace prefix match over the store, so rendering behavior is unchanged.

How did you verify your code works?

• Tested against a copy of my real production database (12 GB, ~1,600 sessions). Without the fix, opening Settings → Workspaces pages through all ~1,600 sessions in serial requests and freezes the whole app for several seconds. With the fix, the page opens instantly and counts/last-active times match the unfixed version.
• bun test src/session/list.test.ts and bun run typecheck in packages/app pass.

Screenshots / recordings

BEFORE

639754013-2c7267c2-2fa2-469e-94dc-152c5ca8cf4e.mov

AFTER

Screen.Recording.2026-08-22.at.01.59.35.mov

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.

[github-actions]

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