feat(digg): rename to 'Digg' and bump per-cluster post limits (#372)

* feat(digg): bump POSTS_PER_CLUSTER to 5 and render limit to 3

Match the per-item enrichment cap and inline-display cap used by the
other sources (Reddit, HN, YouTube, TikTok, GitHub all use 5 fetched /
3 displayed). At the previous 3/2 caps the engine routinely truncated
cluster context — a recent run on cli-printing-press lost the Jason
Calacanis quote tweet entirely because the display cut off after Garry
Tan's first two posts.

* feat(digg): rename 'Digg AI 1000' to 'Digg' in user-facing strings

Drop the 'AI 1000' suffix from the footer line, source label, inline
quote attribution ('via Digg'), why_relevant, container, mock title,
SKILL.md source list, and README sources table. Internal code comments
and docstrings still reference the upstream Digg AI 1000 product.

Bumps version to 3.2.1 and adds a CHANGELOG entry covering this rename
and the POSTS_PER_CLUSTER / render-limit bumps from the prior commit.

---------

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

skills/last30days/scripts/lib/normalize.py

@@ -412,7 +412,7 @@ def _normalize_digg(
     Each cluster is one item. The TLDR carries the most useful body for
     rerank and synthesis. Top-ranked X posts attached at search time are
     passed through under metadata['posts'] so render can emit them as
-    inline 'via Digg AI 1000' quotes.
+    inline 'via Digg' quotes.
     """
     title = str(item.get("title") or "").strip()
     tldr = str(item.get("tldr") or "").strip()
@@ -428,7 +428,7 @@ def _normalize_digg(
         body=body,
         url=str(item.get("url") or f"https://di.gg/ai/{cluster_url_id}"),
         author="",
-        container="Digg AI 1000",
+        container="Digg",
         published_at=item.get("date"),
         date_confidence=_date_confidence(item, from_date, to_date, default="high"),
         engagement=item.get("engagement") or {},