Persist terminal layouts incrementally and reap zmx sessions by attach state

[sbertix]

Why

layouts.json was only written on quit (plus a couple of rare paths), so launching a second instance mid-session (e.g. make run-app) saw a stale snapshot: it pruned tabs the first instance had just opened and terminated their sessions. Two root causes, fixed independently.

Attach-aware zmx reaping

zmx ls --short emits only the session name, so the reaper had no way to tell whether another live instance still had a client attached to a session. We now parse the full ls format (name=/clients=) through a pure, unit-tested ZmxSessionListParser behind a listSessionsWithClients query that returns nil on probe failure.

• reapOrphanSessions and the orphan subset of terminateAllSessions spare any session with a client attached (clients > 0) or an unknown count (nil), so a concurrently-running instance keeps its sessions.
• A failed/timed-out probe reaps nothing (unknown is never killed), while an instance's own tracked sessions are still force-killed on quit.
• Attach state is the authority; layouts.json is only a hint, so this fixes the second-instance-kills-first-instance bug regardless of snapshot freshness.

Incremental layout persistence

A per-worktree debounced markLayoutDirty fires off the settled tab callbacks (create, close, projection drift, removal, rename, selection), captures the freshest snapshot plus live agent records at fire time, updates the in-memory @Shared(.layouts) dict on main, and merges to disk off the main actor.

• LayoutsIncrementalWriter is a single FIFO actor: it re-reads layouts.json, splices in only the keys a flush carries (positive snapshot or explicit delete tombstone), and writes atomically via temp+rename. LayoutsKey.save becomes a no-op so the actor is the sole disk writer.
• Writes are skipped when the splice leaves the dict unchanged, so high-frequency projection ticks under an agent tool-call storm do not churn the file.
• Deletes (prune/archive) bypass the debounce so a queued positive save cannot resurrect a removed worktree; the on-quit synchronous flush stays the terminal write.
• A transient read failure aborts the flush so siblings are not clobbered, while corrupt bytes are rotated aside to layouts.json.corrupt-<timestamp> and persistence recovers, mirroring SidebarPersistenceKey.
• A tab rename now routes through WorktreeTerminalState so a custom title persists incrementally instead of only at quit; the layout-restore path keeps seeding setCustomTitle directly so hydration does not trigger a redundant save.

Fixes along the way

The close-last-surface-via-close_surface path returned without emitting a projection, so onTabRemoved never fired and the closed surface's session was re-orphaned at next launch. It now emits a projection on that branch.

Tests

New coverage for the parser (clients/err/arrow/non-supa/malformed lines), attach-aware reaping (spare attached, skip unknown, kill tracked, nil-probe reaps nothing), and incremental persistence (debounce coalesce, delete-beats-queued-save, no-resurrect-after-prune, flush-on-quit, agent-record-survives-mutation, skip-if-unchanged, corrupt-file rotate-and-recover, rename persists). Full suite green.

[tuist]

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Builds 🔨

Scheme	Status	Duration	Commit
supacode	✅	4m 13s	666c9e25b