Add Wikipedia pageviews as an attention signal

The Wikimedia Pageviews API is public and keyless. For topics with a Wikipedia article, a view-count trend over the window is a cheap 'is public attention rising' signal - one line in the context, not a source list of its own.

Add as an enrichment: resolve the topic to an article title via the Wikipedia search API, fetch daily views for the window, report the trend.

Constraint check: public API, keyless. ✅

No files or tests are named. Start by locating the existing enrichment pipeline and context-signal implementations, then verify the Wikimedia search and Pageviews APIs for the requested window. Done means a matching Wikipedia article is resolved when available, daily views are fetched, and the resulting trend appears as one context line rather than a source entry.

Written by the indexing model from the issue text.