A conversation begun with only a task disappears while its task runs #1482

Seen on dev@debffabf6. Surfaced while verifying #1426; not introduced by it.

What happened

A conversation whose first and only action is /task can vanish from both Home and Sessions after /new moves away, even though its task continues running. It has no title or ordinary user-message row yet, and the project task index receives no entry until the task lands. The running work has no visible route back through either place.

Replication

Deterministic (no model). In a fresh home and temporary Git repository, start a scripted /task whose worker blocks, then invoke /new before it settles. Read Home and Sessions while the worker remains blocked. The conversation is absent from both. Release the worker and observe it appear only after landing.

Field (real models). With OPENROUTER_API_KEY and deepseek/deepseek-v4-flash, start /task as the first action, immediately use /new, and inspect Home and Sessions during a long worker command. Allow several minutes and a few cents.

Where

internal/tui3/home.go:5242 at dev@debffabf6 derives a row name from title and transcript; internal/tui3/place_sessions.go:550, taskSheetOwnRows, relies on the project task index and current-window row. Search internal/session/task_index.go for when a running task first receives an index entry.

The fix

Persist and index a conversation as soon as its task starts, with a placeholder title if necessary, so Home and Sessions can show and reopen it while work is live.

Acceptance

• e2e: through codeaf chat in tmux, /task followed by /new leaves a visible working row in both Home and Sessions until the task settles.
• Unit: first-action task admission writes a discoverable index row before landing.
• Update the Sessions manual and invalidates.