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/pipeline.py

@@ -538,7 +538,7 @@ def _finalize_items_by_source(
         if source == "digg" and items:
             # Pull top-ranked X posts only for the survivors that will appear
             # in the brief. Spending the enrichment budget here (rather than
-            # at retrieval time) keeps the inline 'via Digg AI 1000' quotes
+            # at retrieval time) keeps the inline 'via Digg' quotes
             # paired with the clusters dedupe actually kept.
             digg.enrich_source_items(items, top_k=3)
         finalized[source] = items
@@ -1078,7 +1078,7 @@ def _mock_stream_results(source: str, subquery: schema.SubQuery) -> tuple[list[d
         "digg": [
             {
                 "id": "mock1abc",
-                "title": f"Digg AI 1000 cluster about {subquery.search_query}",
+                "title": f"Digg cluster about {subquery.search_query}",
                 "url": "https://di.gg/ai/mock1abc",
                 "tldr": f"Curated cluster summarizing recent {subquery.search_query} discussion across the AI 1000.",
                 "author": "",