Admin: inline flag-reason popover (replaces prompt())

Per Codex's polish note: flagging a source now opens a small inline popover for
the optional reason (consistent with the calm admin UI) instead of a native
prompt(). Clearing a flag stays immediate. Backdrop/Escape/Cancel close it;
Enter confirms. Optimistic with revert-on-failure, like the other actions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/routes/admin/+page.svelte

@@ -84,18 +84,24 @@
     try { await postJSON(`/api/admin/sources/${s.id}/active`, { active: next }); }
     catch { s.active = next ? 0 : 1; }
   }
-  async function toggleReview(s) {
-    if (s.review_flag) {
-      const prevR = s.review_reason;
-      s.review_flag = 0; s.review_reason = null;
-      try { await postJSON(`/api/admin/sources/${s.id}/review`, { flag: false }); }
-      catch { s.review_flag = 1; s.review_reason = prevR; }
-    } else {
-      const reason = (prompt('Flag this source for review — optional note:') || '').trim();
-      s.review_flag = 1; s.review_reason = reason || null;
-      try { await postJSON(`/api/admin/sources/${s.id}/review`, { flag: true, reason: reason || null }); }
-      catch { s.review_flag = 0; s.review_reason = null; }
-    }
+  // Flagging opens a small inline popover for the reason; clearing is immediate.
+  let flagging = $state(null); // the source being flagged
+  let flagReason = $state('');
+  function openFlag(s) { flagging = s; flagReason = ''; }
+  function cancelFlag() { flagging = null; flagReason = ''; }
+  async function confirmFlag() {
+    const s = flagging;
+    const reason = flagReason.trim() || null;
+    s.review_flag = 1; s.review_reason = reason; // optimistic
+    flagging = null; flagReason = '';
+    try { await postJSON(`/api/admin/sources/${s.id}/review`, { flag: true, reason }); }
+    catch { s.review_flag = 0; s.review_reason = null; }
+  }
+  async function clearReview(s) {
+    const prevR = s.review_reason;
+    s.review_flag = 0; s.review_reason = null; // optimistic
+    try { await postJSON(`/api/admin/sources/${s.id}/review`, { flag: false }); }
+    catch { s.review_flag = 1; s.review_reason = prevR; }
   }
 
   // Feedback inbox: filter + read/unread + delete.
@@ -322,7 +328,7 @@
                 </td>
                 <td class="rowactions">
                   <button class="act" onclick={() => toggleActive(s)}>{s.active ? 'Pause' : 'Resume'}</button>
-                  <button class="act" onclick={() => toggleReview(s)}>{s.review_flag ? 'Clear' : 'Flag'}</button>
+                  <button class="act" onclick={() => (s.review_flag ? clearReview(s) : openFlag(s))}>{s.review_flag ? 'Clear' : 'Flag'}</button>
                 </td>
               </tr>
             {/each}
@@ -465,6 +471,27 @@
   {/if}
 </main>
 
+{#if flagging}
+  <!-- Flag-reason popover: backdrop closes; Escape/Cancel too (keyboard path). -->
+  <!-- svelte-ignore a11y_click_events_have_key_events -->
+  <div class="modal-overlay" role="presentation" onclick={(e) => e.target === e.currentTarget && cancelFlag()}>
+    <div class="modal" role="dialog" aria-modal="true" aria-label="Flag source for review" tabindex="-1">
+      <h3>Flag “{flagging.name}” for review</h3>
+      <p class="msub">An optional note on why — it shows under the source in the table.</p>
+      <input
+        type="text"
+        bind:value={flagReason}
+        placeholder="e.g. acceptance dropping, off-topic lately"
+        onkeydown={(e) => (e.key === 'Enter' ? confirmFlag() : e.key === 'Escape' ? cancelFlag() : null)}
+      />
+      <div class="mbtns">
+        <button class="msend" onclick={confirmFlag}>Flag for review</button>
+        <button class="act" onclick={cancelFlag}>Cancel</button>
+      </div>
+    </div>
+  </div>
+{/if}
+
 <style>
   header.bar { background: var(--surface); border-bottom: 1px solid var(--line); position: sticky; top: 0; z-index: 20; }
   .inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
@@ -614,6 +641,29 @@
   .csend:hover { background: var(--accent-deep); }
   .csend:disabled { opacity: 0.55; cursor: default; }
   .noreply { color: var(--muted); font-size: 0.76rem; font-style: italic; }
+
+  /* Flag-reason popover */
+  .modal-overlay {
+    position: fixed; inset: 0; background: rgba(10, 22, 38, 0.32);
+    display: flex; align-items: center; justify-content: center; padding: 20px; z-index: 60;
+  }
+  .modal {
+    background: var(--surface); border: 1px solid var(--line); border-radius: 16px;
+    box-shadow: 0 12px 34px rgba(40, 38, 28, 0.16); width: 100%; max-width: 420px; padding: 22px 24px;
+  }
+  .modal h3 { margin: 0 0 6px; font-size: 1.2rem; }
+  .modal .msub { margin: 0 0 14px; color: var(--muted); font-size: 0.85rem; }
+  .modal input {
+    width: 100%; box-sizing: border-box; font: inherit; font-size: 0.92rem;
+    padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--bg); color: var(--ink);
+  }
+  .modal input:focus { outline: none; border-color: var(--accent); }
+  .mbtns { display: flex; align-items: center; gap: 12px; margin-top: 14px; }
+  .msend {
+    font: inherit; font-size: 0.85rem; font-weight: 600; background: var(--accent); color: #fff;
+    border: none; border-radius: 999px; padding: 8px 18px; cursor: pointer;
+  }
+  .msend:hover { background: var(--accent-deep); }
   .factions { display: flex; gap: 14px; margin-top: 9px; }
   .factions .act {
     background: none; border: none; padding: 0; cursor: pointer;