feat(web): subtitle lane under the signal chain

web/index.html

@@ -446,6 +446,8 @@
             <p class="module-detail readout" data-role="detail">rpc · grab and seed</p>
           </article>
         </section>
+
+        <section class="chain-lane" id="chain-subs" aria-label="subtitle lane" hidden></section>
       </section>
 
       <section class="deck-group" id="group-roots" hidden aria-labelledby="label-roots">

web/src/health.ts

@@ -9,12 +9,28 @@ export interface Check {
   detail?: string;
 }
 
+/** One enabled subtitle provider (#200). */
+export interface ProviderCheck {
+  id: string;
+  status: CheckStatus;
+  detail?: string;
+}
+
+/** The subtitle lane: providers in use, the selected engine, the binaries. */
+export interface SubtitleHealth {
+  providers: ProviderCheck[];
+  translation?: Check | null;
+  alass: Check;
+  ffmpeg: Check;
+}
+
 export interface HealthReport {
   status: "ok" | "degraded";
   version: string;
   prowlarr: Check;
   transmission: Check;
   tmdb: Check;
+  subtitles: SubtitleHealth;
 }
 
 export type Probe =

web/src/main.ts

@@ -1,4 +1,4 @@
-import { type CheckStatus, type Probe, probeHealth } from "./health";
+import { type Check, type CheckStatus, type Probe, type SubtitleHealth, probeHealth } from "./health";
 import {
   fetchLibrary,
   type LibrarySeries,
@@ -171,6 +171,52 @@ function setModule(refs: ModuleRefs, state: string, tone: Tone, word: string, de
   refs.detail.textContent = detail ?? refs.defaultDetail;
 }
 
+/** One lamp of the subtitle lane (#200): same module shape as the chain,
+ * rendered per poll — which providers are in use is a settings row, not
+ * markup. */
+function subtitleModule(name: string, role: string, check: Check): HTMLElement {
+  const article = document.createElement("article");
+  article.className = "module";
+
+  const head = document.createElement("header");
+  head.className = "module-head";
+  const lamp = document.createElement("span");
+  lamp.className = "lamp";
+  lamp.dataset.state = check.status;
+  const title = document.createElement("h2");
+  title.className = "module-name";
+  title.textContent = name;
+  const status = document.createElement("span");
+  status.className = "module-status readout";
+  status.dataset.tone = TONE_BY_STATUS[check.status];
+  status.textContent = check.status;
+  head.append(lamp, title, status);
+
+  const roleLine = document.createElement("p");
+  roleLine.className = "module-role";
+  roleLine.textContent = role;
+  const detail = document.createElement("p");
+  detail.className = "module-detail readout";
+  detail.textContent = check.detail ?? "";
+
+  article.append(head, roleLine, detail);
+  return article;
+}
+
+function renderSubtitles(subLane: HTMLElement, subs: SubtitleHealth) {
+  const entries: { name: string; role: string; check: Check }[] = subs.providers.map(
+    (provider) => ({ name: provider.id, role: "subtitles in", check: provider }),
+  );
+  if (subs.translation) {
+    entries.push({ name: "translate", role: "engine out", check: subs.translation });
+  }
+  entries.push({ name: "alass", role: "timing sync", check: subs.alass });
+  entries.push({ name: "ffmpeg", role: "track extraction", check: subs.ffmpeg });
+
+  subLane.replaceChildren(...entries.map((entry) => subtitleModule(entry.name, entry.role, entry.check)));
+  subLane.hidden = false;
+}
+
 function must<T extends Element>(selector: string): T {
   const element = document.querySelector<T>(selector);
   if (!element) {
@@ -181,6 +227,7 @@ function must<T extends Element>(selector: string): T {
 
 function main() {
   const chain = must<HTMLElement>(".chain");
+  const subLane = must<HTMLElement>("#chain-subs");
   const masterLamp = must<HTMLElement>("#master-lamp");
   const version = must<HTMLElement>("#version");
 
@@ -235,6 +282,8 @@ function main() {
       for (const name of ["tmdb", "prowlarr", "master"] as const) {
         setTrace(name, null);
       }
+      subLane.hidden = true;
+      subLane.replaceChildren();
       return;
     }
 
@@ -259,6 +308,7 @@ function main() {
         setTrace(name, TONE_BY_STATUS[check.status]);
       }
     }
+    renderSubtitles(subLane, report.subtitles);
   }
 
   let inFlight = false;

web/src/style.css

@@ -315,6 +315,17 @@ body {
 
 /* ---- modules --------------------------------------------------------- */
 
+/* The subtitle lane (#200): one lamp per upstream actually in use, rendered
+   by the health poll under the main chain. Same module vocabulary, no bus —
+   these feed the reconcile loop, not each other. */
+.chain-lane {
+  margin-top: var(--space-6);
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr));
+  gap: var(--space-4);
+  align-items: stretch;
+}
+
 .module {
   background: var(--panel);
   border: 1px solid var(--line);