feat(pkm): daily notes + workspace search + doc-aware Q&A

Three more features from the brainstorm menu, built on a shared search
algorithm so the codebase stays small.

- src/main/DailyNotes.js — Zettelkasten-style helper. One YYYY-MM-DD.md
  per local date under <userData>/notes/daily/; loads skeleton from
  <userData>/notes/templates/daily.md when present (built-in default
  otherwise). openOrCreate never clobbers existing content.
- src/main/WorkspaceSearch.js — tag/wikilink-aware content search.
  Pure module, injectable-IO tested. Query grammar: bare words,
  #tag, @wikilink, "quoted phrases". Facets weight +3 each; prose
  terms +1/occurrence capped at 5; edits within 7 days get a recency
  nudge. Returns ranked results with snippets.
- src/main/DocQA.js — chunk-level Q&A wrapper over WorkspaceSearch.
  cleanQuestion strips question words (what/how/why/...) and verb
  noise (write/read/show/tell/...) so they don't drown the ranking.
  Returns top-K passages instead of whole-file hits — multiple chunks
  from the same file can appear in the answer.
- src/main.js — IPC: daily-notes:open-today, daily-notes:list,
  workspace-search:query, doc-qa:ask. Path validation through the
  existing validatePath gate; a global Ctrl+Alt+D shortcut creates
  today's daily note from anywhere.
- src/preload.js — all four channels added to ALLOWED_SEND_CHANNELS.

Tests (56 new across the three modules):
- tests/main/DailyNotes.test.js (15): dateKey formatting, pathFor,
  template load + {date}/{weekday} substitution, openOrCreate +
  no-clobber, nested-dir creation, listExisting filtering,
  isValidDir rejects NUL/non-string.
- tests/main/WorkspaceSearch.test.js (25): parseQuery grammar,
  hasTag/hasWikilink word boundaries, scoreDocument scoring,
  per-term spam cap, recency nudge, search ranking + limit +
  empty-query short-circuit, bad-input safety.
- tests/main/DocQA.test.js (16): cleanQuestion stripping + facet
  preservation, chunkDocument paragraph + hard-split, ask()
  top-K, recency tiebreaker, missing-files fallback.

Full suite: 748 tests pass, 66 suites, lint+format clean.

Amit Haridas

tests/main/PDFOperations.test.js

@@ -54,8 +54,7 @@ describe('PDFOperations - Task 15 new operations', () => {
       expect(result.success).toBe(true);
       expect(result.text).toContain('Hello Task 15 Page One');
       expect(result.text).toContain('Second Page Content');
-    }, // First pdfjs-dist legacy import can exceed the 5s default on slower
-    // CI runners (observed on windows-latest)
+    }, // CI runners (observed on windows-latest) // First pdfjs-dist legacy import can exceed the 5s default on slower
     30000);
 
     it('returns failure for a nonexistent file', async () => {