tui: session picker only shows sessions from the 50 most recently updated across all projects

Summary

The TUI session picker requests the 50 most recently updated sessions across all projects (GET /api/session with no parameters) and then filters them client-side by the current directory. In an active multi-project setup, any session older than the newest ~50 sessions globally becomes unreachable from the picker — the session exists, the server can return it, but the TUI never asks for it and offers no server-side search. This makes old sessions look "lost" (a frequent report in this repo), especially after upgrading or migrating sessions.

Environment

• opencode version: 2.0.1
• OS: macOS (Darwin 27.0.0, arm64)
• Terminal: WezTerm (xterm-256color, truecolor)
• Shell: /bin/zsh
• Install/channel: local, v2 line
• Active plugins: none (plugins: [])

Reproduction

1. Have a project with a session last updated 2+ days ago (project A), and work in other projects so that 50+ sessions across all projects get updated more recently.
2. Open the TUI in project A and open the session list.
3. The old session of project A does not appear.

Instrumentation (all verified on my machine):

• Server log shows the TUI issues GET /api/session with no query parameters.
• The bare endpoint returns the 50 most recently updated sessions globally (time range of the response was "today only", while the DB contains 1000+ sessions).
• The TUI then filters that response client-side by directory: only the single session created today in the current project remains visible.
• The server API itself is correct — GET /api/session?directory=<cwd> returns all sessions of the project including old ones, and GET /api/session?directory=<cwd>&search=<term> finds old sessions by title.
• The picker's filter is client-side only: the server log contains no ?search= or ?cursor= requests from the TUI, so typing in the picker cannot reach sessions outside the loaded 50.

Concretely: a session updated 2 days ago was the 51st+ newest globally (96 sessions updated after it), so it was invisible in the TUI of its own project, while opencode session list (per-project, default 100) and the directory-scoped API both returned it immediately.

Expected Behavior

The session picker should list sessions scoped to the current project/directory (matching opencode session list behavior), and/or perform server-side search across all sessions of the project instead of filtering only the already-loaded 50.

Actual Behavior

The picker shows only the intersection of (globally 50 most recently updated sessions) × (current directory). In active multi-project usage this quickly becomes just "today's sessions", and older sessions are unreachable through the TUI.

Additional Context

• Workaround: opencode -s <session-id> and opencode session list work correctly per project; also opencode api get "/api/session?directory=$PWD&search=..." can locate old session IDs.
• Discovered while investigating a V1→V2 migration report of "disappearing sessions": the data was intact in opencode.db and correctly migrated; the picker was simply never requesting it.
• Related reports (same user-visible symptom, different angles): #39064 (after update, /sessions only shows today's sessions), #46832 (Desktop search only covers the loaded subset), #46123 (feature request: configurable list limit / show all).

Happy to provide additional log excerpts if useful.