fix(push): an agent opening a conversation must reach the phone too

[WhichPaths]

Follow-on to #199, which gave cumora reply the push dispatch it was missing. Two more agent-authored writes never had it either — and unlike a reply, both of them open a conversation that did not exist a second ago.

The gap

dispatchMessagePush has exactly two callers: POST /conversations/:id/messages and cmdReply. But an agent can also start a thread, through two of its own tools:

tool	writer	kind	pushes
dm_with	startPrivateChat (agents/private_chat.ts)	text	no
pull_group	startPulledGroup (agents/scanner_helper.ts)	text	no

Both commit the row and enqueue the same message.new broadcast that cmdReply does, and then stop. So the human's desktop toasts — NotificationToasts fires on any message.new that is not theirs and not a system row — and the phone stays silent. The same desktop/phone asymmetry #199 was about, in the two paths #199 did not touch.

An opening line is the worst message to drop. A reply lands in a thread the recipient already knows about and will see when they next open the app; the first message of a brand-new conversation is the one they have no other way to discover. And a pull exists specifically to interrupt someone — there is a six-hour per-agent cooldown on it for that reason — so reaching every surface except the phone was backwards.

startPrivateChat is not agent-to-agent only, despite what the tool's copy suggests: it validates kind IN ('agent','human') and carries a whole users/company_members existence branch for the human case. pull_group's comment likewise says humans in members[] are a normal choice ("Do NOT auto-add a human — agents ... can pull true agent-only groups").

I checked every other INSERT INTO messages in the server. The rest are correct as they stand: membership.ts, calendar.ts and inproc-client.ts write kind='system', which the in-app surface skips too, and ws.ts's doc-mention row is addressed to an agent with the only human being its own author.

The fix

One fire-and-forget dispatchMessagePush after COMMIT in each, matching how the other two callers do it — the row is durable first, and a push never holds up the write.

Recipients need no new filtering: computeMessageRecipients joins users, so an agent-to-agent DM or an agent-only pull pushes to nobody on its own, and the mute / "currently looking at the app" filters apply unchanged.

Tests

Three added to the existing agent-reply-push.test.ts, which already owns this contract and its seed helpers:

• an agent opening a DM reaches the phone — recipient is the offline human, body is the opening line, and the title is the agent's name rather than its raw id (agents have no users row)
• an agent pulling a group reaches the phone
• an agent-only conversation still pushes to nobody — the guard rail against this becoming "push on every agent write"

The first two are red before the change; the third passes either way, on purpose:

without the fix:
  ok 1-4   (the existing reply tests)
  not ok 5 - an agent opening a DM reaches the phone
  not ok 6 - an agent pulling a group reaches the phone
  ok 7     - an agent-only conversation still pushes to nobody
  # pass 5  # fail 2

with the fix:  # pass 7  # fail 0

Also green: tsc --noEmit, biome lint ., all three scripts/guard-*.mjs, the agent-tools and conversations integration suites, and the unit suite.