Add feed/reader mode with full-article capture at ingest

Reader mode presents the stories on a page one at a time in a focused
overlay, marking each read as it's shown. Left/right arrows (or the header
book button / `f`) page through them; read stories dim on the grid. Read
state is device-local in localStorage.

Backing this required actually capturing article bodies, which Pete wasn't
doing — it kept only the RSS <description> lede and discarded content:encoded:

- stories.content column (idempotent migration; old rows fall back to lede)
- parser keeps content:encoded as paragraph-preserving text
- article fetch already done for paywall detection now also returns its body,
  so ingest stores the richer of feed-content vs scraped body with no extra
  request (prefers the archive snapshot body for paywalled stories)
- GET /api/article?id= serves the stored text; card queries now select id and
  expose it as data-id for the reader

Tests cover content extraction, the storage round-trip, and the article
endpoint + card rendering end to end.

internal/web/handlers.go

@@ -17,6 +17,7 @@ const pageSize = 24
 
 // StoryView is the trimmed-down record used in templates.
 type StoryView struct {
+	ID         int64
 	Headline   string
 	Lede       string
 	ImageURL   string
@@ -30,6 +31,7 @@ type StoryView struct {
 
 func toView(s storage.Story) StoryView {
 	return StoryView{
+		ID:         s.ID,
 		Headline:   s.Headline,
 		Lede:       s.Lede,
 		ImageURL:   s.ImageURL,
@@ -334,6 +336,31 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 	_ = json.NewEncoder(w).Encode(map[string]any{"results": results})
 }
 
+// handleArticle serves the stored full text of a single story for reader mode.
+// The client already has headline/image/source/time from the card's data
+// attributes, so this returns just the body text (and the lede as a fallback
+// for stories ingested before content was captured).
+func (s *Server) handleArticle(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.Header().Set("Cache-Control", "no-store")
+	id, err := strconv.ParseInt(strings.TrimSpace(r.URL.Query().Get("id")), 10, 64)
+	if err != nil || id <= 0 {
+		http.Error(w, `{"error":"bad id"}`, http.StatusBadRequest)
+		return
+	}
+	content, lede, found, err := storage.GetStoryReaderText(id)
+	if err != nil {
+		slog.Error("web: article read failed", "id", id, "err", err)
+		http.Error(w, `{"error":"internal error"}`, http.StatusInternalServerError)
+		return
+	}
+	if !found {
+		http.Error(w, `{"error":"not found"}`, http.StatusNotFound)
+		return
+	}
+	_ = json.NewEncoder(w).Encode(map[string]any{"content": content, "lede": lede})
+}
+
 func shortTimeAgo(t time.Time) string {
 	d := time.Since(t)
 	switch {