feat: warn on the main window when Best-FaceID cannot do anything

Best-FaceID reads identity from an identity_pin-tagged guide, and only the AUTO
continuity builder ever applies that tag (timeline._identity_pin_guide). Every
way of losing it is silent: the run succeeds and simply carries no identity.

Three such states, all verified against _run_sampler_inputs (tagged guides in
the emitted funpack_scene_guides payload: 2 when healthy, 0 in each bad case):
  - no identity pin set at all
  - custom guide stack on -- manual guides REPLACE auto guides (`manual or auto`),
    and manual GuideEntry has no identity_pin field, so the pin is dropped
  - auto continuity off -- same outcome by the other route

Shown on the main window of both frontends, not inside the settings pane that
turns it on: you would only see it there if you already went looking.
  - shared predicate: PipelineCaps.identityTransferIssue -> {short, detail}
  - Editor:   amber chip beside Generate in the timeline header, click opens
              Engine settings; full text in the tooltip
  - Easy Gen: full-width amber strip between the preview and the Generate row

fpActionbar had to grow the identity fields -- it hashed only pid/sel/gen, so
setting the pin would have left a stale warning sitting next to Generate.

Verified live in both UIs across all five transitions (no pin -> pin -> stack on
-> stack off -> auto off -> feature off); appears and clears correctly in each.
Silent when the Chain Sampler is not in the pipeline, where the knob is inert.

Tests: 22 failed / 465 passed, unchanged from baseline.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

easy_gen/frontend/app.js

@@ -15,6 +15,7 @@
   const uploadInput = document.getElementById("easy-upload-input");
   const galleryBtn = document.getElementById("easy-gallery-btn");
   const generateBtn = document.getElementById("easy-generate-btn");
+  const warnStrip = document.getElementById("easy-warn-strip");
   const advancedBtn = document.getElementById("easy-advanced-btn");
   const projectsBtn = document.getElementById("easy-projects-btn");
   const saveBtn = document.getElementById("easy-save-btn");
@@ -72,6 +73,12 @@
     uploadBtn.textContent = attached ? "⬆ Uploaded ✕" : "⬆ Upload";
     preview.setUpload(attached ? API.mediaUrl(source.media_ref) : null, source?.type === "v2v" ? "video" : "image");
 
+    // A setting that is switched on but cannot do anything belongs on the main screen,
+    // above Generate — not only inside the pane that switched it on.
+    const issue = window.PipelineCaps?.identityTransferIssue(st);
+    warnStrip.textContent = issue ? issue.detail : "";
+    warnStrip.hidden = !issue;
+
     const pid = p ? p.id : null;
     if (pid !== lastProjectId) {
       lastProjectId = pid;

easy_gen/frontend/easy.css

@@ -63,6 +63,15 @@ a.brand:hover .brand-sub { color: var(--amber-2); }
   overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
 .easy-progress-stop:disabled { opacity: .6; cursor: default; }
 
+/* Full-width notice between the preview and the Generate row: a setting that is on
+   but cannot do anything should be readable without opening any panel. */
+.easy-warn-strip {
+  flex: none; padding: 9px 16px; font-size: 12.5px; line-height: 1.45;
+  color: var(--amber); border-top: 1px solid color-mix(in srgb, var(--amber) 45%, var(--line));
+  background: color-mix(in srgb, var(--amber) 9%, transparent);
+}
+.easy-warn-strip[hidden] { display: none; }
+
 .easy-bar {
   flex: none; display: flex; align-items: flex-end; gap: 12px;
   padding: 14px 16px; border-top: 1px solid var(--line); background: var(--ink-1);

easy_gen/frontend/index.html

@@ -64,6 +64,8 @@
 
     <main class="easy-preview" id="easy-preview"></main>
 
+    <div class="easy-warn-strip" id="easy-warn-strip" hidden></div>
+
     <footer class="easy-bar">
       <button class="btn ghost easy-upload-btn" id="easy-upload-btn" type="button"
         title="Upload an image or video to guide generation">⬆ Upload</button>

movie_editor/frontend/actionbar.js

@@ -40,6 +40,17 @@
     montageBtn.disabled = !hasProject() || busy(st);
     montageBtn.onclick = () => window.MontageDialog?.open();
     mount.append(montageBtn);
+
+    // Settings that are switched on but cannot do anything belong next to Generate,
+    // not buried in the pane that switched them on — you would only see it there if
+    // you already went looking.
+    const issue = window.PipelineCaps?.identityTransferIssue(st);
+    if (issue) {
+      const chip = el("button", "btn ghost compact action-warn", "⚠ " + issue.short);
+      chip.title = issue.detail + "\n\nClick to open Engine settings.";
+      chip.onclick = () => window.SettingsWindow?.open("engine");
+      mount.append(chip);
+    }
   }
 
   if (window.ViewBus) window.ViewBus.subscribeActionbar(render);

movie_editor/frontend/pipeline_caps.js

@@ -60,6 +60,43 @@
     return sourceNeedsAnchorMedia(scene, st);
   }
 
+  // Best-FaceID reads identity from an identity_pin-tagged guide, and ONLY the auto
+  // continuity builder ever applies that tag (backend timeline._identity_pin_guide).
+  // Every way of losing it is silent — the run succeeds carrying no identity at all —
+  // so the main window says so before you spend a generation finding out.
+  // Returns {short, detail} for a compact chip and a full-width strip respectively,
+  // or null when the setting will actually do something.
+  function identityTransferIssue(st) {
+    const p = st && st.project;
+    if (!p || !(p.sampler_inputs || {}).identity_transfer_enabled) return null;
+    if (!usesChainSampler(st)) return null;   // knob is inert without the Chain Sampler
+    const cs = p.continuity_settings || {};
+    const gs = p.guide_settings || {};
+    if (!cs.identity_pin_ref) {
+      return {
+        short: "Best-FaceID: no identity pin",
+        detail: "You have Best-FaceID enabled but no identity pin is set — it has no face to transfer. "
+          + "Set the identity pin in Settings → Engine → Continuity, or press 📌 on an image in the Media bin.",
+      };
+    }
+    if (gs.stack_enabled) {
+      return {
+        short: "Best-FaceID: pin not reaching sampler",
+        detail: "You have Best-FaceID enabled and an identity pin set, but the custom guide stack replaces "
+          + "the auto-continuity guides that carry the pin — so the pin never reaches the sampler. "
+          + "Turn the custom guide stack off in Settings → Engine → Continuity.",
+      };
+    }
+    if (cs.auto_enabled === false) {
+      return {
+        short: "Best-FaceID: pin not reaching sampler",
+        detail: "You have Best-FaceID enabled and an identity pin set, but auto continuity is off — the pin "
+          + "only travels with auto-continuity guides. Turn auto continuity on in Settings → Engine → Continuity.",
+      };
+    }
+    return null;
+  }
+
   function sourceLabel(type) {
     const map = {
       empty: "Empty · text-to-video",
@@ -82,6 +119,7 @@
     defaultSceneSourceType,
     sourceNeedsAnchorMedia,
     isMissingAnchorMedia,
+    identityTransferIssue,
     sourceLabel,
   };
 })();

movie_editor/frontend/styles.css

@@ -197,6 +197,9 @@ button, input, select, textarea { font-family: inherit; color: var(--text); }
 .btn.ghost { background: transparent; border-color: transparent; color: var(--muted); padding: 4px 8px; font-size: 12px; }
 .btn.ghost:hover { color: var(--amber-2); background: var(--ink-3); }
 .btn.ghost.on { color: var(--amber); border-color: color-mix(in srgb, var(--amber) 55%, var(--line)); }
+/* "This is switched on but cannot do anything" chip, shown beside Generate. */
+.btn.action-warn { color: var(--amber); border-color: color-mix(in srgb, var(--amber) 45%, var(--line)); background: color-mix(in srgb, var(--amber) 10%, transparent); }
+.btn.action-warn:hover { color: var(--amber-2); border-color: var(--amber); }
 .btn.danger:hover { border-color: var(--danger); color: var(--danger); }
 .btn.tiny { padding: 2px 7px; font-size: 12px; }
 

movie_editor/frontend/view_bus.js

@@ -120,6 +120,14 @@
       pid: st.project?.id,
       sel: st.selectedSceneIds?.length,
       gen: st.gen?.state,
+      // The Best-FaceID warning chip lives in this zone, so everything its message
+      // depends on has to be part of the fingerprint — otherwise setting the pin
+      // leaves a stale warning sitting next to Generate.
+      idOn: st.project?.sampler_inputs?.identity_transfer_enabled,
+      idPin: st.project?.continuity_settings?.identity_pin_ref,
+      idAuto: st.project?.continuity_settings?.auto_enabled,
+      idStack: st.project?.guide_settings?.stack_enabled,
+      sampler: st.project?.sampler_slot,
     });
   }