fix: stop nameMatchBonus awarding a spurious +10 on a whitespace-only query

[JOhnsonKC201]

Summary

nameMatchBonus (search ranking, src/search/query-utils.ts) awards a spurious flat +10 "name match" bonus to every node when the query is empty or whitespace-only.

The bug

The function collapses the query into a single comparable token and then checks startsWith:

const queryLower = query.replace(/[\s]+/g, '').toLowerCase();
...
if (nameLower.startsWith(queryLower)) {
  const ratio = queryLower.length / nameLower.length;
  return Math.round(10 + 30 * ratio);   // → 10 when queryLower === ''
}

For an empty / whitespace-only query, queryLower is '', and in JS anyString.startsWith('') is always true. So the branch fires for every node, with ratio = 0, returning Math.round(10 + 0) = 10 — a uniform, undeserved name-match bonus for a query that matches no name at all.

Reachability

This is reachable end-to-end through the public searchNodes API:

• searchNodes(' ') → parseQuery(' ') yields text = '', while the raw query is ' ' (truthy).
• The rescoring guard in src/db/queries.ts is if (results.length > 0 && (text || query)), so a whitespace-only query passes the guard ('' || ' ' → truthy).
• scoringQuery = text || query = ' ' is then handed to nameMatchBonus(name, ' ') for every candidate.

scorePathRelevance already handles this case correctly (it returns 0 for a whitespace-only query); nameMatchBonus did not.

The fix

A one-line early guard, before the always-true startsWith('') check:

if (!queryLower) return 0;

Repro / tests

Added a nameMatchBonus empty/whitespace query block to __tests__/context-ranking.test.ts:

expect(nameMatchBonus('authenticate', '')).toBe(0);     // was 10
expect(nameMatchBonus('authenticate', '   ')).toBe(0);  // was 10
expect(nameMatchBonus('authenticate', 'authenticate')).toBe(80); // unchanged — guard isn't over-broad

• Before the fix: the empty/whitespace cases return 10 (test fails).
• After the fix: they return 0, and a real exact-match query is unaffected.

Verification

• npx vitest run __tests__/context-ranking.test.ts __tests__/search-query-parser.test.ts → 39 passed.
• Confirmed the new tests fail on main (stash the source change → expected 10 to be 0) and pass with it.
• tsc --noEmit clean.

Diff is two files, +31/-4. No behavior change for any non-empty query.