feat(domain): add SourceRateLimited transcript source

429 from the caption endpoint means the IP is rate-limited (retry later),
not that the video has no captions. Distinguishing it from SourceNone is the
prerequisite for the runner's backoff/retry logic.

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

internal/domain/domain.go

@@ -18,6 +18,12 @@ type TranscriptSource string
 const (
 	SourceCaptions TranscriptSource = "captions"
 	SourceNone     TranscriptSource = "none"
+	// SourceRateLimited records that the caption endpoint returned HTTP 429.
+	// Unlike SourceNone (a permanent absence), this is a transient "retry later":
+	// the IP is rate-limited, not the video caption-less. It carries no text
+	// (HasText is false), so the engine degrades the same as SourceNone, but the
+	// runner persists it distinctly to retry after a backoff window.
+	SourceRateLimited TranscriptSource = "rate_limited"
 )
 
 // User is the Tapir-side profile. At Stage 0 there is exactly one.

internal/web/view.go

@@ -535,6 +535,11 @@ a.btn, a.btn:visited { color: var(--accent-fg); }
 .empty { text-align: center; color: var(--muted); padding: var(--s5) var(--s4); border: 1px dashed var(--line); border-radius: var(--radius); background: var(--card); }
 .empty strong { display: block; color: var(--fg); font-size: 1.05rem; margin-bottom: var(--s2); }
 .empty code { background: var(--accent-weak); color: var(--accent); padding: .1rem .35rem; border-radius: .3rem; }
+.empty p { margin: var(--s3) 0 0; }
+/* connected-but-empty: a distinct accent callout, not a muted blank state, so a
+   fresh account knows the next step is to run tapir, not "something is broken". */
+.empty-connected { border-style: solid; border-color: var(--accent); background: var(--accent-weak); color: var(--fg); }
+.empty-connected strong { color: var(--accent); }
 
 /* flash / notification banner */
 .flash { padding: var(--s2) var(--s3); border-radius: var(--radius); margin-bottom: var(--s4); font-size: .92rem; border: 1px solid var(--line); }

internal/web/views.templ

@@ -79,12 +79,12 @@ templ flashBanner(code string) {
 // #summary-list region; a non-HTMX request renders the whole page. flash carries
 // a one-shot notification (e.g. "connected", "registered") surfaced on arrival
 // after a POST→redirect.
-templ ListPage(rows []store.SummaryRow, f Filter, flash string) {
+templ ListPage(rows []store.SummaryRow, f Filter, flash string, hasConnected bool) {
 	@Layout("Tapir — Summaries") {
 		@flashBanner(flash)
 		@filterForm(f)
 		<div id="summary-list">
-			@summaryList(rows)
+			@summaryList(rows, hasConnected)
 		</div>
 	}
 }
@@ -110,12 +110,20 @@ templ filterForm(f Filter) {
 // summaryList is the swappable list fragment: one card per video (summarized or
 // not). Cards reflow to a single column on mobile; an empty list shows a friendly
 // first-run state instead of a blank table.
-templ summaryList(rows []store.SummaryRow) {
+templ summaryList(rows []store.SummaryRow, hasConnected bool) {
 	if len(rows) == 0 {
+		if hasConnected {
+			<div class="empty empty-connected">
+				<strong>Your YouTube account is connected!</strong>
+				<span>Run <code>tapir run</code> to discover your subscriptions. Videos will appear here once discovered. In manual mode, each new video gets a Summarize button.</span>
+			</div>
+		} else {
 			<div class="empty">
 				<strong>No videos yet</strong>
-			<span>Videos appear here as your subscriptions are processed — run <code>tapir run</code> to fetch them. In manual mode, use the Summarize button to queue one.</span>
+				<span>Connect your YouTube account to get started.</span>
+				<p><a class="btn" href="/oauth/youtube/connect">Connect YouTube</a></p>
 			</div>
+		}
 	} else {
 		<ul class="cards">
 			for _, r := range rows {