Add hybrid search with filtering and recency boost

Introduces SearchOptions interface with folder/tag filters, exact phrase
matching via quoted queries, and optional recency boosting with configurable
half-life. Replaces pure semantic or keyword search with a combined scoring
model: keyword scores are blended with semantic results, then adjusted by
filters and recency. Adds mtime to vault index entries and expands test
coverage for the new options.

tests/vault-indexer.test.ts

@@ -286,8 +286,8 @@ describe('VaultIndexer', () => {
         basename: 'test',
         path: 'test.md',
       } as any);
-      const score = (indexer as any).calculateWeightedScore(tokenized, queryTokens);
-      expect(score.score).toBe(0);
+      const score = (indexer as any).calculateWeightedScore(tokenized, queryTokens, []);
+      expect(score).toBe(0);
     });
 
     it('should score higher when more tokens match', () => {
@@ -300,13 +300,15 @@ describe('VaultIndexer', () => {
       const query2 = 'algorithm design pattern';
       const score1 = (indexer as any).calculateWeightedScore(
         tokenized,
-        (indexer as any).tokenize(query1)
+        (indexer as any).tokenize(query1),
+        []
       );
       const score2 = (indexer as any).calculateWeightedScore(
         tokenized,
-        (indexer as any).tokenize(query2)
+        (indexer as any).tokenize(query2),
+        []
       );
-      expect(score2.score).toBeGreaterThan(score1.score);
+      expect(score2).toBeGreaterThan(score1);
     });
 
     it('should be case insensitive', () => {
@@ -318,9 +320,10 @@ describe('VaultIndexer', () => {
       const query = 'important algorithm';
       const score = (indexer as any).calculateWeightedScore(
         tokenized,
-        (indexer as any).tokenize(query)
+        (indexer as any).tokenize(query),
+        []
       );
-      expect(score.score).toBeGreaterThan(0);
+      expect(score).toBeGreaterThan(0);
     });
 
     it('should handle word boundary matching', () => {
@@ -332,9 +335,10 @@ describe('VaultIndexer', () => {
       const query = 'algorithm';
       const score = (indexer as any).calculateWeightedScore(
         tokenized,
-        (indexer as any).tokenize(query)
+        (indexer as any).tokenize(query),
+        []
       );
-      expect(score.score).toBeGreaterThan(0);
+      expect(score).toBeGreaterThan(0);
     });
   });
 
@@ -392,4 +396,97 @@ describe('VaultIndexer', () => {
       expect(tokenized.firstParagraph).not.toContain('Second');
     });
   });
+
+  describe('extractExactPhrases', () => {
+    it('should extract quoted phrases', () => {
+      const phrases = (indexer as any).extractExactPhrases('search "exact phrase" here');
+      expect(phrases).toEqual(['exact phrase']);
+    });
+
+    it('should extract multiple quoted phrases', () => {
+      const phrases = (indexer as any).extractExactPhrases('"phrase one" and "phrase two"');
+      expect(phrases).toEqual(['phrase one', 'phrase two']);
+    });
+
+    it('should return empty array when no quotes', () => {
+      const phrases = (indexer as any).extractExactPhrases('no quotes here');
+      expect(phrases).toEqual([]);
+    });
+  });
+
+  describe('searchVault with options', () => {
+    it('should boost exact phrase matches', async () => {
+      const file1: MockTFile = { basename: 'a', path: 'a.md' };
+      const file2: MockTFile = { basename: 'b', path: 'b.md' };
+      mockVault.getMarkdownFiles = jest.fn().mockReturnValue([file1, file2]);
+      mockVault.read = jest
+        .fn()
+        .mockResolvedValueOnce('The quick brown fox jumps over the lazy dog')
+        .mockResolvedValueOnce('The quick brown fox');
+
+      const results = await indexer.searchVault('"lazy dog"', 5);
+      // The file with the exact phrase should rank higher
+      expect(results.length).toBeGreaterThan(0);
+      if (results.length >= 2) {
+        expect(results[0].score).toBeGreaterThanOrEqual(results[1].score);
+      }
+    });
+
+    it('should filter by folder', async () => {
+      const file1: MockTFile = { basename: 'a', path: 'Projects/a.md' };
+      const file2: MockTFile = { basename: 'b', path: 'Archive/b.md' };
+      mockVault.getMarkdownFiles = jest.fn().mockReturnValue([file1, file2]);
+      mockVault.read = jest
+        .fn()
+        .mockResolvedValueOnce('important keyword here')
+        .mockResolvedValueOnce('completely unrelated text');
+
+      const results = await indexer.searchVault('important keyword', 5, { folder: 'Projects' });
+      expect(results.length).toBe(1);
+      expect(results[0].path).toBe('Projects/a.md');
+    });
+
+    it('should filter by tag', async () => {
+      const file1: MockTFile = { basename: 'a', path: 'a.md' };
+      const file2: MockTFile = { basename: 'b', path: 'b.md' };
+      mockVault.getMarkdownFiles = jest.fn().mockReturnValue([file1, file2]);
+      mockVault.read = jest
+        .fn()
+        .mockResolvedValueOnce('---\ntags: idea\n---\nimportant keyword')
+        .mockResolvedValueOnce('---\ntags: done\n---\nother unrelated content');
+
+      const results = await indexer.searchVault('important keyword', 5, { tag: 'idea' });
+      expect(results.length).toBe(1);
+      expect(results[0].path).toBe('a.md');
+    });
+
+    it('should apply recency boost', async () => {
+      const now = Date.now();
+      const file1: MockTFile = { basename: 'a', path: 'a.md' };
+      const file2: MockTFile = { basename: 'b', path: 'b.md' };
+      mockVault.getMarkdownFiles = jest.fn().mockReturnValue([file1, file2]);
+      mockVault.read = jest
+        .fn()
+        .mockResolvedValueOnce('important keyword')
+        .mockResolvedValueOnce('important keyword');
+
+      // Mock stat with different mtimes
+      (file1 as any).stat = { mtime: now - 86400000 }; // 1 day ago
+      (file2 as any).stat = { mtime: now - 86400000 * 100 }; // 100 days ago
+
+      const results = await indexer.searchVault('important keyword', 5, { recencyBoost: true });
+      expect(results.length).toBe(2);
+      // The more recent file should have a higher score
+      expect(results[0].score).toBeGreaterThanOrEqual(results[1].score);
+    });
+
+    it('should build a cache key with options', () => {
+      const key1 = (indexer as any).buildCacheKey('test', 5, { folder: 'Projects', tag: 'idea' });
+      expect(key1).toContain('folder:Projects');
+      expect(key1).toContain('tag:idea');
+
+      const key2 = (indexer as any).buildCacheKey('test', 5, { recencyBoost: false });
+      expect(key2).toContain('norecency');
+    });
+  });
 });