[Desktop] Add advanced task/conversation search with date, project, mode, and status filters

What feature would you like to see?

Please make task/conversation history in the unified ChatGPT/Codex desktop app substantially easier to search and recover.

The current history/search experience is adequate for recent threads, but becomes difficult once a user has many long-lived Chat, Work, Codex, local, remote, CLI, and IDE sessions. In particular, finding a thread from a known time period is much harder than it should be.

Requested search/filter capabilities

At minimum, history search should support:

• Date/time filters: created before/after, updated before/after, or a date range.
• Project/workspace filters.
• Product mode / surface: Chat, Work, Codex.
• Runtime/source where applicable: Desktop, VS Code, CLI, remote/mobile.
• Local vs remote.
• Active vs archived.
• Sorting by created time, last updated, and relevance.
• Search by exact thread/task ID when one is known.

A useful UI could combine free-text search with filter chips, for example:

Search: "training crash"
Date: 2026-08-01 ... 2026-08-15
Project: robotics
Mode: Codex
Status: archived
Sort: last updated

Important correctness requirement

Search should operate over the complete accessible history, not only a recent-window subset. A thread falling out of a "recent N" list should not make it effectively undiscoverable.

This matters for long-running research and engineering work where a user may remember roughly when a task happened but not its exact title or wording.

Why this matters

For users with hundreds of tasks, history is not just a convenience feature; it is part of the working memory of the product. A weak retrieval surface forces users to keep external notes, manually scroll, or remember thread titles.

Date filtering is especially important because "I worked on this last Tuesday / two weeks ago / before a release" is a common human retrieval cue.

Suggested acceptance criteria

1. A user can filter tasks by an arbitrary created/updated date range.
2. A user can combine date filters with project/workspace, mode, source, and archive status.
3. Search results are not limited to only the most recent visible threads.
4. Sorting by created/updated time is supported.
5. The same history item has a stable identity regardless of which client originally created it.
6. Old threads remain discoverable even after they leave the default recent list.

Related issues

• #21244 — VS Code history intermittently hides existing local chats.
• #25319 — scope/group/filter VS Code chats by current workspace/project.

Those are narrower reliability/scoping issues; this request is for a first-class advanced history retrieval UI across the unified desktop experience.

No implementation files or tests are named. Start by locating the unified desktop history/search entry point, then review related issues #21244 and #25319 for existing scope. Done means the listed filters, sorting, stable history identity, and discovery of older threads are supported across the stated clients.