fix(container): gate poll loop on trigger=1 to honor accumulate contract

A warm container picks up every pending messages_in row on each poll tick
and calls markProcessing → agent.query → markCompleted. Before this, that
included trigger=0 rows (ignored_message_policy='accumulate' context),
causing the agent to wake and potentially respond to messages the wiring
had explicitly opted out of engaging on — defeating accumulate's "store
as context, don't engage" contract.

Gate the main poll loop with `messages.some(m => m.trigger === 1)` —
mirrors host-side countDueMessages which is already gated. If the batch
has no wake-eligible row, sleep and leave them pending. They ride along
via the same getPendingMessages query the next time a real trigger=1
lands, which is the intended accumulate behavior.

The concurrent active-turn poll (line ~290) is unchanged on purpose —
once the agent has engaged, pushing in accumulate rows mid-turn as
additional context is desired.

initTestSessionDb was missing the trigger and series_id columns on
messages_in, out of sync with the live migration. Added both so the new
tests (and any future trigger-aware tests) can run.

Four tests cover the data contract: trigger=0 rows are returned by
getPendingMessages (so they ride along), the gate predicate correctly
identifies accumulate-only batches, mixed batches pass the gate, and the
schema default of 1 applies when the column is omitted.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

container/agent-runner/src/db/connection.ts

@@ -157,7 +157,9 @@ export function initTestSessionDb(): { inbound: Database; outbound: Database } {
       status         TEXT DEFAULT 'pending',
       process_after  TEXT,
       recurrence     TEXT,
+      series_id      TEXT,
       tries          INTEGER DEFAULT 0,
+      trigger        INTEGER NOT NULL DEFAULT 1,
       platform_id    TEXT,
       channel_type   TEXT,
       thread_id      TEXT,