* perf(terminal): defer cold worktree activation tab mounts until first reveal
Activating a worktree mounted a TerminalPane for every saved terminal tab
in one render pass. Each mount replays scrollback through xterm, attaches
a WebGL renderer, and issues a sync-IPC snapshot read, so a worktree with
many agent-session tabs froze the renderer for tens of seconds (field
trace: 200+ replay-guard stall releases inside one activation window,
plus restore-marker feedback loops re-fetching snapshots at ~4/sec).
Cold activations now mount only the tabs the user can see (active tab,
each split group's active tab, activity-portal tabs, pending spawns) plus
tabs that are already live or that parked byte watchers cannot cover.
Every other tab defers like a cold-parked tab from birth: no view until
first reveal, with the parked byte watchers owning bell/title/completion
side effects meanwhile. The restriction reuses the targeted background
mount mechanism and lifts once every tab has been revealed.
Deferral only engages when more than four tabs would mount cold, and only
while hidden-view parking is enabled, so small worktrees and the parking
kill switch keep today's behavior.
* test(terminal): prove cold-activation deferral end-to-end; unblock it past hydration's blanket spawn flag
The new e2e (child worktree, 8 tabs, renderer reload against live daemon
sessions) caught the deferral never engaging: session hydration marks
every persisted tab pendingActivationSpawn, and treating that flag as
must-mount-now put all tabs in the immediate set. Only explicit queued
startups (pendingStartupByTabId) mount eagerly; a deferred tab's reveal
consumes the hydration flag exactly like an activation mount would.
Sleep/wake respawn flows go through targeted background mounts and are
unaffected (terminal-sleep-wake-restore passes).
The spec asserts the visible tab mounts, deferred tabs stay unmounted
with parked byte-watcher coverage, and a revealed tab mounts on demand.
* fix(terminal): harden deferred activation lifecycle
* docs(reliability): correct SSH startup assertion evidence
9d51732523