homepage: bento 3-up + 300x600 inline; word-safe excerpt; bigger sponsor logos

- FeaturedBentoFromDb: row below the hero is now a 3-up rail on the left
  with the Blackmagic 300x600 on the right, aligned with the hero's right
  edge. SidebarAdStack skips that 300x600 so the article-feed sidebar
  starts with the 300x250 stack instead.
- cleanExcerpt: render-time word-snap for excerpts that were hard-cut at a
  byte count (Matrox 50-years showed "Since 1976, the co" mid-word). Used
  on the bento hero subhead and the article-feed cards.
- SponsorLogoStrip: now also pulls every tracked_companies.featured=true
  brand (Rode, TBC Consoles, Plura, Autocue, Autoscript, Filmcraft,
  Lectrosonics, Prompter People, SanDisk, Sennheiser), and logos go from
  h-10/h-12 max-w-140 → h-14/h-16 max-w-180 with thicker padding.

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

src/lib/articles/excerpt.ts

@@ -0,0 +1,21 @@
+// Render-time excerpt sanitizer. Some imported / AI-generated excerpts were
+// hard-truncated at a fixed byte count, leaving sentences clipped mid-word
+// (e.g. "Since 1976, the co"). Until the upstream excerpt generator gets the
+// same treatment, this helper makes any clipped excerpt visually clean:
+// strip trailing junk, snap to the last complete word, and append an
+// ellipsis only when the excerpt isn't already a complete sentence.
+
+const SENTENCE_END = /[.!?…]['")\]]?$/;
+const TRAILING_JUNK = /[\s,;:—–\-—_]+$/;
+
+export function cleanExcerpt(raw: string | null | undefined): string {
+  if (!raw) return "";
+  let s = raw.replace(/ /g, " ").trim();
+  if (!s) return "";
+  if (SENTENCE_END.test(s)) return s;
+  // Drop the trailing partial token.
+  const lastSpace = s.lastIndexOf(" ");
+  if (lastSpace > 20) s = s.slice(0, lastSpace);
+  s = s.replace(TRAILING_JUNK, "");
+  return s + "…";
+}