fix(sessions): persist queued follow-ups across restart and offline

[gantoine]

Problem

A follow-up message queued while a cloud agent was running was lost on app restart, and an offline follow-up was thrown away entirely:

• messageQueue lived only in the in-memory, non-persisted session store — a restart wiped it with no rehydration path.
• sendPrompt threw on offline before enqueuing, so an offline follow-up surfaced only as a toast and was gone.

Changes

• New durable queuedMessageStore (electronStorage-backed), mirrored from the core session store via a subscription so every queue mutation is captured — including the several UI call sites that mutate the store directly (dock remove, steer/queue toggle, cancel-into-editor) that a service-seam wrapper would miss. Reconciles-before-mirroring per task so a freshly-created empty session can't wipe not-yet-seeded messages; rehydrates persisted follow-ups when a session reappears.
• Offline cloud follow-ups queue (and persist) instead of being thrown away; the composer stays enabled with a clarifying tooltip.
• Non-destructive local drain — sendQueuedMessages rolls back via prependQueuedMessages on send failure instead of silently dropping messages.
• Durable queue + tracking wiped on logout / project switch (avoids leaking follow-ups across accounts).

Tests

Queued-message store cap/clear/empty-removal, offline cloud queueing. Typecheck and Biome pass.

Note

Independent of (and splittable from) the cloud-run resilience PR.

---

Created with PostHog Code

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 5e0c364.}

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix(sessions): persist queued follow-ups..." | Re-trigger Greptile}

[greptile-apps]

_hasHydrated never set on first run or cleared storage

When electronStorage has no data for this key (first run or post-clearAll), zustand-persist calls onRehydrateStorage with (undefined, undefined) — no error, but state is also undefined. The else branch evaluates state?.setHasHydrated(true) as a no-op, so _hasHydrated stays false forever. Every subsequent call to whenHydrated() in reconcileTask creates a store subscriber that never resolves and is never garbage-collected — one per session creation, accumulating for the process lifetime.

Suggested change

	onRehydrateStorage: () => (state, error) => {
	if (error) {
	useQueuedMessageStore.getState().setHasHydrated(true);
	} else {
	state?.setHasHydrated(true);
	}
	},
	onRehydrateStorage: () => (state, error) => {
	if (error || !state) {
	useQueuedMessageStore.getState().setHasHydrated(true);
	} else {
	state.setHasHydrated(true);
	}
	,

[greptile-apps]

Two independent behaviours in one it block

The "clears a single task and clears all" test verifies both clear(taskId) and clearAll() in sequence; a failure in the first assertion makes the second unreachable and the root cause ambiguous. Splitting these into two tests (and preferring parameterised form for the cap-boundary cases, per the project's convention) would make test failures self-describing.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!