Move local /resume cwd filtering into thread/list

[canvrno-oai]

Move local resume and fork cwd filtering to thread/list instead of filtering in the TUI. This makes the /resume menu feel slightly faster to load when working in repos with many historical threads, and centralizes the cwd filtering in app-server.

Affected:

• /resume from inside the TUI.
• codex resume with no session ID and without --last
• codex resume --all
• codex fork with no session ID and without --last
• codex fork --all

Not affected:

• codex resume
• codex fork
• codex resume --last
• codex fork --last

Steps to test performance improvement in a real Codex environment:

• Launch codex resume using compiled binary in a directory that has seen many threads.
• Launch codex resume using release binary in same directory.
• Observe difference in time-to-full-page as threads load.

[etraut-openai]

A nice code cleanup! It also appears to improve performance of the resume picker in the tui.

I built locally and ran it through some manual tests to look for regressions, and I didn't find any problems.