channels: mount Slack HTTP receiver on shared Bun.serve (#103)

* channels: mount Slack HTTP receiver on shared Bun.serve

The HTTP-mode Slack channel was binding ExpressReceiver to the same
port as Phantom's main Bun.serve listener. The bind silently failed,
the router caught the rejection, and /slack/* never came up; live
canary traffic verified `POST /slack/events` returned 404 and
`/health.channels.slack` was false.

Refactor SlackHttpChannel into a Bolt App driven by a tiny
BunReceiver whose start/stop are no-ops. The three Slack ingress
paths now mount on the existing Bun.serve via slack-http-routes.ts;
the channel exposes handleEvent, handleInteractivity, and
handleCommand, each running the existing slack-gateway-verifier
guard before dispatching the parsed body into app.processEvent.

The verifier file is unchanged. Slash commands (urlencoded with
top-level team_id) are picked up by a small extractor in the
dispatcher so the third Slack endpoint can satisfy team-id binding
without touching the verifier.

Tests cover the verifier guard happy and failure paths via real
Request objects, plus a hermetic Bun.serve test that proves the
routes are alive end-to-end.

* channels: gate slack-http dispatch on channel.isConnected() (Codex P1)

The provider is wired in src/index.ts during channel setup before
router.connectAll() runs, so inbound POSTs arriving in the startup
window dispatched into a half-initialized channel. The gate also
covers the post-disconnect() path (state flips to "disconnected")
and the auth-failure path (state flips to "error").

Both 503 paths return JSON. Slack retries 503 up to 3 times within
5 minutes per the inbound contract, so the gate resolves naturally.

+3 tests pinning the not-yet-connected case, the post-disconnect
sibling case (audit doc inline), and the same gate on /slack/interactivity.

* channels: race processEvent against ack in dispatchToBolt (Codex round 2 P1+P2)

Previously dispatchToBolt awaited input.app.processEvent before returning,
but Bolt's processEvent resolves only when listener middleware finishes,
not when ack() fires. Phantom's Slack listener calls runtime.handleMessage
which routinely outlasts Slack's ~3s ack window, so /slack/events stayed
open past the deadline and triggered Slack-side retries. The catch path
also called ackFn() with no args, which resolves to 200 and silently
suppressed listener failures.

Replace the await + try/catch with Promise.race over three tagged
outcomes: ack winner returns the listener's response immediately,
processEvent rejecting before ack surfaces as 500 so Slack retries, and
processEvent resolving without any ack falls back to a 200 with an
operator warning (defense against a hypothetical Bolt regression). The
async listener work continues in the background, matching the previous
HTTPReceiver processBeforeResponse=false semantics.

Tests: +3 covering long-running listener (handler returns 200 while
listener continues), processEvent rejects before ack (handler 500),
and processEvent resolves without ack (handler 200 + warning). Total
1971 pass, typecheck and lint clean. File at 294 lines (under 300
channels/ budget).

Author: mcheemaa

src/channels/__tests__/slack-channel-factory.test.ts

@@ -125,7 +125,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "socket",
 			channelsConfig: null,
-			port: 3100,
 		});
 		expect(ch).toBeNull();
 	});
@@ -137,7 +136,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "socket",
 			channelsConfig: disabled,
-			port: 3100,
 		});
 		expect(ch).toBeNull();
 	});
@@ -146,7 +144,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "socket",
 			channelsConfig: SOCKET_CONFIG,
-			port: 3100,
 		});
 		expect(ch).toBeInstanceOf(SlackChannel);
 	});
@@ -158,7 +155,6 @@ describe("createSlackChannel", () => {
 			createSlackChannel({
 				transport: "http",
 				channelsConfig: null,
-				port: 3100,
 				identityFetcher: idFetcher,
 				secretsFetcher: secFetcher,
 			}),
@@ -171,7 +167,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "http",
 			channelsConfig: null,
-			port: 3100,
 			identityFetcher: idFetcher,
 			secretsFetcher: secFetcher,
 		});
@@ -190,7 +185,6 @@ describe("createSlackChannel", () => {
 		await createSlackChannel({
 			transport: "http",
 			channelsConfig: null,
-			port: 3100,
 			identityFetcher: idFetcher,
 			secretsFetcher: secFetcher,
 		});
@@ -211,7 +205,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "http",
 			channelsConfig: SOCKET_CONFIG,
-			port: 3100,
 			identityFetcher: idFetcher,
 			secretsFetcher: secFetcher,
 		});
@@ -232,7 +225,6 @@ describe("createSlackChannel", () => {
 		const ch = await createSlackChannel({
 			transport: "http",
 			channelsConfig: null,
-			port: 3100,
 			metadataBaseUrl: "http://gateway.test",
 			identityFetcher: idFetcher,
 			secretsFetcher: secFetcher,