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/DocQA.test.js

@@ -0,0 +1,136 @@
+/**
+ * @jest-environment node
+ *
+ * DocQA tests — pure module, no IO. Verifies the question→chunks pipeline.
+ */
+const DocQA = require('../../src/main/DocQA');
+
+describe('DocQA.cleanQuestion', () => {
+  test('strips question words but keeps substantive terms', () => {
+    expect(DocQA.cleanQuestion('what did I write about rust async')).toBe('rust async');
+    expect(DocQA.cleanQuestion('how do I configure pandoc')).toBe('configure pandoc');
+  });
+
+  test('keeps #tags and @wikilinks intact', () => {
+    expect(DocQA.cleanQuestion('what is #rust about?')).toContain('#rust');
+    expect(DocQA.cleanQuestion('tell me about @project-x')).toContain('@project-x');
+  });
+
+  test('keeps "quoted phrases" intact', () => {
+    const out = DocQA.cleanQuestion('what does "rust async" mean?');
+    expect(out).toContain('"rust async"');
+  });
+
+  test('returns empty string for non-string input', () => {
+    expect(DocQA.cleanQuestion(null)).toBe('');
+    expect(DocQA.cleanQuestion(undefined)).toBe('');
+    expect(DocQA.cleanQuestion(42)).toBe('');
+  });
+
+  test('returns empty string when only question words remain', () => {
+    expect(DocQA.cleanQuestion('what is this?')).toBe('');
+  });
+});
+
+describe('DocQA.chunkDocument', () => {
+  test('returns [] for empty / non-string input', () => {
+    expect(DocQA.chunkDocument('')).toEqual([]);
+    expect(DocQA.chunkDocument(null)).toEqual([]);
+  });
+
+  test('returns one chunk for a short document', () => {
+    const chunks = DocQA.chunkDocument('hello world');
+    expect(chunks).toHaveLength(1);
+    expect(chunks[0].text).toBe('hello world');
+  });
+
+  test('respects paragraph breaks', () => {
+    const content = 'para one.\n\npara two.\n\npara three.';
+    const chunks = DocQA.chunkDocument(content);
+    expect(chunks.length).toBeGreaterThanOrEqual(1);
+    expect(chunks[0].text).toContain('para one');
+  });
+
+  test('splits long content into multiple chunks', () => {
+    const big = 'x'.repeat(2500);
+    const chunks = DocQA.chunkDocument(big, 800);
+    expect(chunks.length).toBeGreaterThan(1);
+    // Each chunk should be ≤ 800 chars (except possibly the last)
+    for (let i = 0; i < chunks.length - 1; i++) {
+      expect(chunks[i].text.length).toBeLessThanOrEqual(800);
+    }
+  });
+});
+
+describe('DocQA.ask', () => {
+  const files = [
+    {
+      path: '/notes/rust.md',
+      content:
+        'Rust is a systems language.\n\nAsync in Rust uses tokio for runtime.\n\nBorrow checker enforces memory safety.',
+    },
+    {
+      path: '/notes/pandoc.md',
+      content: 'Pandoc is a document converter.\n\nConfiguration uses YAML metadata blocks.',
+    },
+    {
+      path: '/notes/old.md',
+      content: 'Old notes from years ago.',
+    },
+  ];
+
+  test('returns empty chunks for a question with no substantive terms', () => {
+    const r = DocQA.ask({ question: 'what is this?', files });
+    expect(r.chunks).toEqual([]);
+  });
+
+  test('returns empty chunks when no files match', () => {
+    const r = DocQA.ask({ question: 'quantum entanglement', files });
+    expect(r.chunks).toEqual([]);
+  });
+
+  test('returns relevant chunks for a substantive question', () => {
+    const r = DocQA.ask({ question: 'how does rust async work', files, topK: 3 });
+    expect(r.chunks.length).toBeGreaterThan(0);
+    // The first hit should be from rust.md (highest relevance)
+    expect(r.chunks[0].filePath).toBe('/notes/rust.md');
+    expect(r.chunks[0].snippet).toMatch(/rust|async|tokio/i);
+    expect(r.chunks[0].score).toBeGreaterThan(0);
+  });
+
+  test('honors topK', () => {
+    const r = DocQA.ask({ question: 'rust', files, topK: 2 });
+    expect(r.chunks.length).toBeLessThanOrEqual(2);
+  });
+
+  test('includes the original question in the response', () => {
+    const r = DocQA.ask({ question: 'how do I configure pandoc', files });
+    expect(r.question).toBe('how do I configure pandoc');
+  });
+
+  test('handles missing or empty file list gracefully', () => {
+    const r = DocQA.ask({ question: 'rust', files: [] });
+    expect(r.chunks).toEqual([]);
+
+    const r2 = DocQA.ask({ question: 'rust', files: null });
+    expect(r2.chunks).toEqual([]);
+  });
+
+  test('rank prefers recent edits when scores tie (recency nudge)', () => {
+    const now = Date.now();
+    const filesWithMtime = [
+      {
+        path: '/fresh.md',
+        content: 'rust language overview',
+        mtimeMs: now - 1 * 24 * 60 * 60 * 1000, // 1 day ago
+      },
+      {
+        path: '/stale.md',
+        content: 'rust language overview (same text)',
+        mtimeMs: now - 60 * 24 * 60 * 60 * 1000, // 60 days ago
+      },
+    ];
+    const r = DocQA.ask({ question: 'rust overview', files: filesWithMtime, topK: 5 });
+    expect(r.chunks[0].filePath).toBe('/fresh.md');
+  });
+});