feat(webhooks): channel reactions/startOn, session-target deliveries, and a data-plane DB seam

Bundles the uncommitted webhook work (entangled across shared files, so committed together):

- Channels: a startOn session-start gate (only summon a new session on matching
  events, otherwise resume), agent and lifecycle reactions, Slack mrkdwn conversion,
  and a mentions() helper in @trigger.dev/slack.
- Deliveries UI links the chat.agent session as the delivery target.
- Webhook database seam: an injected webhookPrisma (writer) and webhookReplica
  (reader) so the whole webhook feature (WebhookEndpoint + WebhookDelivery) can move
  to a dedicated Postgres by config. Prep only and connection-neutral until
  WEBHOOK_DATABASE_URL is set; narrow WebhookDatabase types keep control-plane tables
  off the webhook client, with a two-DB test as the runtime backstop.

Author: ericallam

.changeset/webhook-channel-reactions.md

@@ -0,0 +1,23 @@
+---
+"@trigger.dev/core": patch
+"@trigger.dev/sdk": patch
+"@trigger.dev/slack": patch
+"trigger.dev": patch
+---
+
+More control over `chat.agent` channels. A channel can now gate when a *new* session starts with `startOn`, so an agent only engages on the events you choose (e.g. a Slack mention) and otherwise just continues the existing thread. The `@trigger.dev/slack` package adds a `mentions()` helper for the mention predicate, converts the agent's markdown reply into Slack mrkdwn, and only routes real user messages (system messages like channel joins no longer trigger a turn).
+
+Agents can also react to the triggering message. Lifecycle reactions signal turn state (one while working, swapped to done, or error on failure), and the agent can react itself from `run()`:
+
+```ts
+import { slack, mentions } from "@trigger.dev/slack";
+
+slack({
+  id: "support",
+  token: process.env.SLACK_BOT_TOKEN,
+  startOn: mentions("U012BOT"),
+  reactions: { working: ["eyes", "hourglass_flowing_sand"], done: "white_check_mark", error: "x" },
+});
+```
+
+Each lifecycle reaction is a single emoji, an array (one picked at random per turn), or a function of the event. Inside `run()`, `channel?.react("white_check_mark")` reacts on demand.

apps/webapp/app/components/webhookDeliveries/v1/DeliveriesTable.tsx

@@ -1,5 +1,7 @@
 import { ArrowRightIcon } from "@heroicons/react/20/solid";
 import { useLocation, useNavigation } from "@remix-run/react";
+import { AIChatIcon } from "~/assets/icons/AIChatIcon";
+import { RunsIcon } from "~/assets/icons/RunsIcon";
 import { WebhookIcon } from "~/assets/icons/WebhookIcon";
 import { DateTime } from "~/components/primitives/DateTime";
 import { MiddleTruncate } from "~/components/primitives/MiddleTruncate";
@@ -21,7 +23,12 @@ import { useEnvironment } from "~/hooks/useEnvironment";
 import { useOrganization } from "~/hooks/useOrganizations";
 import { useProject } from "~/hooks/useProject";
 import { type WebhookDeliveryListItem } from "~/presenters/v3/WebhookDetailPresenter.server";
-import { v3RunPath, v3WebhookDeliveryPath, v3WebhookTaskPath } from "~/utils/pathBuilder";
+import {
+  v3RunPath,
+  v3SessionPath,
+  v3WebhookDeliveryPath,
+  v3WebhookTaskPath,
+} from "~/utils/pathBuilder";
 import { cn } from "~/utils/cn";
 import { DeliveryStatusBadge } from "./DeliveryStatus";
 
@@ -61,7 +68,7 @@ export function DeliveriesTable({
           <TableHeaderCell>Delivery</TableHeaderCell>
           <TableHeaderCell>Status</TableHeaderCell>
           <TableHeaderCell>External delivery ID</TableHeaderCell>
-          <TableHeaderCell>Run</TableHeaderCell>
+          <TableHeaderCell>Target</TableHeaderCell>
           <TableHeaderCell>Created</TableHeaderCell>
           <TableHeaderCell>Processed</TableHeaderCell>
           <TableHeaderCell>Error</TableHeaderCell>
@@ -89,6 +96,14 @@ export function DeliveriesTable({
                 })
               : undefined;
 
+            // Session deliveries route to a session (their run is just its current turn), so the
+            // session is the meaningful target; task deliveries fall back to the run.
+            const sessionPath = delivery.session
+              ? v3SessionPath(organization, project, environment, {
+                  friendlyId: delivery.session.friendlyId,
+                })
+              : undefined;
+
             const webhookPath = delivery.webhook
               ? v3WebhookTaskPath(organization, project, environment, delivery.webhook.slug)
               : undefined;
@@ -132,9 +147,17 @@ export function DeliveriesTable({
                     <span className="text-text-dimmed">None</span>
                   )}
                 </TableCell>
-                <TableCell to={runPath}>
-                  {delivery.run ? (
-                    <span className="font-mono text-xs">{delivery.run.friendlyId}</span>
+                <TableCell to={sessionPath ?? runPath}>
+                  {delivery.session ? (
+                    <span className="flex items-center gap-x-1">
+                      <AIChatIcon className="size-4 text-sessions" />
+                      <span className="font-mono text-xs">{delivery.session.friendlyId}</span>
+                    </span>
+                  ) : delivery.run ? (
+                    <span className="flex items-center gap-x-1">
+                      <RunsIcon className="size-4 text-runs" />
+                      <span className="font-mono text-xs">{delivery.run.friendlyId}</span>
+                    </span>
                   ) : (
                     <span className="text-text-dimmed">None</span>
                   )}
@@ -163,7 +186,11 @@ export function DeliveriesTable({
                     <span className="text-text-dimmed">None</span>
                   )}
                 </TableCell>
-                <DeliveryActionsCell deliveryPath={deliveryPath} runPath={runPath} />
+                <DeliveryActionsCell
+                  deliveryPath={deliveryPath}
+                  runPath={runPath}
+                  sessionPath={sessionPath}
+                />
               </TableRow>
             );
           })
@@ -186,9 +213,11 @@ export function DeliveriesTable({
 function DeliveryActionsCell({
   deliveryPath,
   runPath,
+  sessionPath,
 }: {
   deliveryPath: string;
   runPath?: string;
+  sessionPath?: string;
 }) {
   return (
     <TableCellMenu
@@ -201,6 +230,14 @@ function DeliveryActionsCell({
             leadingIconClassName="text-webhooks"
             title="View delivery"
           />
+          {sessionPath ? (
+            <PopoverMenuItem
+              to={sessionPath}
+              icon={ArrowRightIcon}
+              leadingIconClassName="text-runs"
+              title="View session"
+            />
+          ) : null}
           {runPath ? (
             <PopoverMenuItem
               to={runPath}