sessions: pre-project-row sessions stranded in global project are hidden from session lists #57629

Summary

Sessions created before their directory's project row exists are stored under the global
project (worktree /) and never appear in project-scoped session listings (opencode session list, TUI session list), even when the session's directory matches the current directory
exactly. An entire 120-session history was invisible; only sessions created after the project
row appeared were listed.

Environment

• opencode version: 2.1.1
• OS: Linux 6.18.40.1-microsoft-standard-WSL2+ (linux x64)
• Terminal: TERM=xterm-256color (TERM_PROGRAM/COLORTERM unset)
• Shell: /usr/bin/zsh
• Install/channel: latest
• Active plugins: none found (global/project config declare no plugins; no .opencode/plugin(s)/)

Reproduction

1. From /home/redacted, create sessions while project has no row for that directory
   (sessions are stored with project_id='global').
2. Later start opencode in /home/redacted again so a project row for it is created
   (observed: created when a new session started).
3. Run opencode session list --format json from /home/redacted.
4. Only sessions created after the row existed are returned; all older sessions — including
   ones whose directory is exactly /home/redacted — are absent even with -n 500.

Expected Behavior

Directory-scoped session listings should include sessions whose directory matches the
current directory regardless of which project bucket stored them, or older sessions should be
re-scoped to the directory's project row when it is first created.

Actual Behavior

opencode session list from /home/redacted returned exactly 1 session while session_v2
contained 141: 120 in project_id='global' (53 with directory=/home/redacted, 67 with
directory=/home/redacted/redacted) and 21 in the /home/redacted project. Listing from
/home/redacted/redacted returned 0 despite 67 sessions with that exact directory, because
that directory has no project row of its own. GET /api/session returns all sessions
regardless of project, so the data exists but is unreachable from directory-scoped views.

Additional Context

• Frequency: user hit this previously and assumed the history was lost; reproducible whenever
  sessions predate their directory's project row.
• Evidence: project_directory was empty; re-pointing the 120 rows with
  UPDATE session_v2 SET project_id = '<directory project>' WHERE project_id='global'
  (after an online backup) made session list -n 500 return all 118 top-level sessions — the
  rows were intact; only the bucket was wrong.
• Workaround requires direct DB editing; session export/import re-creates sessions instead
  of fixing the association.
• Related quirk: starting opencode in a subdirectory creates a new project row there,
  stranding those sessions from the opposite direction.