fix(dashboard): F-U-003 surface known collection patterns on the Files page

The Files page could only list a collection if the operator already
knew its name and typed it in. No "browse known collections" affordance,
no backend endpoint listing collections.

Closest approximation without new backend: pull registered files-trigger
collection_globs from the existing triggers list and surface them as:
- a <datalist> on the collection input for autocomplete
- chip buttons under the form that one-click set the input

Empty state copy points the operator at the Triggers tab. Backend
endpoint to list known collections directly is still a v1.1.10+ task.

Styling uses the F-U-004 :root tokens so it inherits the dark theme.

AUDIT.md anchor: F-U-003 (frontend-only; backend endpoint deferred).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/routes/apps/[slug]/files/+page.svelte

@@ -14,6 +14,11 @@
 	let error = $state<string | null>(null);
 	let fileToRemove = $state<FileMeta | null>(null);
 	let removing = $state(false);
+	/// F-U-003: hints derived from registered `files` triggers. No
+	/// backend endpoint lists known collections; this is the next-best
+	/// approximation — operators see "we've heard about these patterns"
+	/// instead of having to guess.
+	let collectionHints = $state<string[]>([]);
 
 	async function loadApp() {
 		try {
@@ -23,9 +28,25 @@
 		}
 	}
 
+	async function loadCollectionHints() {
+		try {
+			const r = await api.triggers.list(slug);
+			const seen = new Set<string>();
+			for (const t of r.triggers) {
+				if (t.details.kind === 'files' && t.details.collection_glob) {
+					seen.add(t.details.collection_glob);
+				}
+			}
+			collectionHints = Array.from(seen).sort();
+		} catch {
+			collectionHints = [];
+		}
+	}
+
 	$effect(() => {
 		void slug;
 		void loadApp();
+		void loadCollectionHints();
 	});
 
 	async function loadFiles(cursor?: string) {
@@ -102,12 +123,36 @@
 	>
 		<label>
 			<span>Collection</span>
-			<input bind:value={collection} placeholder="avatars" required />
+			<input
+				bind:value={collection}
+				placeholder="avatars"
+				list="files-collection-hints"
+				required
+			/>
 		</label>
+		<datalist id="files-collection-hints">
+			{#each collectionHints as h}
+				<option value={h}></option>
+			{/each}
+		</datalist>
 		<button type="submit" disabled={loading || !collection.trim()}>
 			{loading ? 'Loading…' : 'List files'}
 		</button>
 	</form>
+	{#if collectionHints.length > 0}
+		<p class="hint">
+			Known collection patterns from registered files triggers:
+			{#each collectionHints as h, i}
+				{#if i > 0}, {/if}
+				<button class="hint-chip" type="button" onclick={() => (collection = h)}>{h}</button>
+			{/each}
+		</p>
+	{:else}
+		<p class="hint">
+			No files triggers registered yet. Once you register a files trigger from the Triggers tab,
+			its collection glob will appear here as a suggestion.
+		</p>
+	{/if}
 
 	{#if error}
 		<div class="error">{error}</div>
@@ -217,10 +262,28 @@
 		font-size: 0.78rem;
 	}
 	.muted {
-		color: var(--muted, #666);
+		color: var(--text-muted);
+	}
+	.hint {
+		color: var(--text-muted);
+		font-size: 0.85rem;
+		margin: 0.5rem 0 1rem;
+	}
+	.hint-chip {
+		background: var(--bg-elevated);
+		color: var(--text-primary);
+		border: 1px solid var(--border);
+		border-radius: 0.25rem;
+		padding: 0.1rem 0.4rem;
+		font-size: 0.8rem;
+		cursor: pointer;
+		font-family: monospace;
+	}
+	.hint-chip:hover {
+		border-color: var(--color-link);
 	}
 	.error {
-		color: #b00020;
+		color: var(--color-danger);
 		margin: 0.5rem 0;
 	}
 	button.danger {