NSID suggestions include non-record lexicons (queries, procedures, defs) #50

Problem #

The Target Lexicon NSID suggestions in the "Create a record" and "Update a record" actions include lexicons that can't be record targets, such as searchStarterPacks, unmuteActor and graph.defs.

Code: app/routes/api/lexicons/suggest.ts. It returns every NSID that matches the prefix, with no filtering by lexicon type.

Fix direction #

• Filter suggestions to lexicons whose main definition has type: "record".
• Decide where to filter: in collectLocalNsids, collectCachedNsids and collectRemoteNsids in lexicons/discovery.ts, or on the merged set in the route. The remote source may need a schema fetch, so check the cost.
• Add route tests for each source.

Context #

Split out of #46 so the focus-loss fix could ship on its own. Replacing the native <datalist> with a non-intrusive combobox (the other half of #20) stays out of scope here. Related: #20