Keep search, geo and metrics output lossless

[tamnd]

What and why

The search, geo and metrics commands decoded only a subset of what their
APIs return, so -o json/-o jsonl could not reconstruct the original
record. This is the last domain in the losslessness sweep.

Each struct is widened to the full property set, and the request asks for it
(gsprop, clprop, rvprop, llprop, wider siprop). Table and download
views are unchanged; where a column needs a flat string, an accessor method
covers it (e.g. Revision.TagsLine()). Presence-only keys (primary,
hidden, writeapi) and the number-or-string dim decode through
json.RawMessage.

Coverage

• search / related / random keep page id, key, matched_title, thumbnail
• geosearch keeps page id, ns, primary, type, name, dim, country, region, globe
• revisions keep user id, parsed comment, sha1; tags become an array
• categories keep sort key, prefix, timestamp, hidden; members keep page id
• langlinks keep langname; backlinks keep page id
• pageviews keep per-item project/article/access/agent/granularity; top keeps article key/project/access/date
• stats widens siteinfo with server, paths, software versions, wiki id, server time, jobs

Before / after

Before, search emitted only title, description, snippet, url. After:

{"title":"Alan Turing","pageid":1208,"key":"Alan_Turing","description":"English computer scientist (1912–1954)","snippet":"...","thumbnail":{"url":"//upload.wikimedia.org/.../60px-Alan_turing_header.jpg","mimetype":"image/jpeg","width":60,"height":80},"url":"https://en.wikipedia.org/wiki/Alan_Turing"}

Before, geosearch emitted only title, lat, lon, dist, url. After:

{"pageid":9232,"title":"Eiffel Tower","lat":48.85822,"lon":2.2945,"dist":19.8,"primary":true,"dim":1000,"country":"FR","region":"75","url":"https://en.wikipedia.org/wiki/Eiffel_Tower"}

revisions now carries userid, sha1 and a tags array; stats reports
the server, paths, versions, wiki id and server time.

Tests

wiki/search_geo_metrics_test.go decodes representative API blobs and asserts
the new fields survive (thumbnail/key, geo props with presence primary and
string dim, revision user id + tags array, category sortkey/hidden,
langname, wider siteinfo, pageview context). go test ./... green, golangci-lint clean. Verified live against the API.