feat: MVP-4 Sprint 1 - Query parser, real-time search, keyboard navigation

- Add query-parser.ts with AST for type:, tag:, is:favorite, is:pinned filters
- Integrate parser into search API
- Add real-time search with 300ms debounce in search-bar
- Add keyboard navigation (↑↓ Enter ESC) for Spotlight-like UX
- Add dropdown results display with loading state
- Add 22 tests for query parser

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/query-parser.ts

@@ -0,0 +1,61 @@
+export interface QueryAST {
+  text: string
+  filters: {
+    type?: string
+    tag?: string
+    isFavorite?: boolean
+    isPinned?: boolean
+  }
+}
+
+const FILTER_REGEX = /(tag|type):(\S*)/gi
+const IS_FAVORITE_REGEX = /\bis:favorite\b/gi
+const IS_PINNED_REGEX = /\bis:pinned\b/gi
+
+export function parseQuery(query: string): QueryAST {
+  if (!query || typeof query !== 'string') {
+    return { text: '', filters: {} }
+  }
+
+  const filters: QueryAST['filters'] = {}
+
+  // Extract type: filter
+  const typeMatches = query.matchAll(/(?:^|\s)(type):(\S*)/gi)
+  for (const match of typeMatches) {
+    const value = match[2]
+    if (value) {
+      filters.type = value
+    }
+  }
+
+  // Extract tag: filter
+  const tagMatches = query.matchAll(/(?:^|\s)(tag):(\S*)/gi)
+  for (const match of tagMatches) {
+    const value = match[2]
+    if (value) {
+      filters.tag = value
+    }
+  }
+
+  // Check for is:favorite (case insensitive filter name)
+  const isFavoriteMatches = query.match(/\bis:favorite\b/i)
+  if (isFavoriteMatches) {
+    filters.isFavorite = true
+  }
+
+  // Check for is:pinned (case insensitive filter name)
+  const isPinnedMatches = query.match(/\bis:pinned\b/i)
+  if (isPinnedMatches) {
+    filters.isPinned = true
+  }
+
+  // Remove all filter patterns from the query to get remaining text
+  let text = query
+    .replace(FILTER_REGEX, '')
+    .replace(IS_FAVORITE_REGEX, '')
+    .replace(IS_PINNED_REGEX, '')
+    .trim()
+    .replace(/\s+/g, ' ')
+
+  return { text, filters }
+}

src/lib/search.ts

@@ -1,10 +1,13 @@
 import { prisma } from '@/lib/prisma'
 import stringSimilarity from 'string-similarity'
 import { getUsageStats } from '@/lib/usage'
+import { parseQuery, QueryAST } from '@/lib/query-parser'
 
 export interface SearchFilters {
   type?: string
   tag?: string
+  isFavorite?: boolean
+  isPinned?: boolean
 }
 
 export interface ScoredNote {
@@ -133,10 +136,19 @@ async function scoreNote(
 }
 
 export async function noteQuery(
-  query: string,
+  queryOrAST: string | QueryAST,
   filters: SearchFilters = {}
 ): Promise<ScoredNote[]> {
-  const queryLower = query.toLowerCase().trim()
+  // Support both old signature (query string + filters) and new (QueryAST)
+  let queryAST: QueryAST
+  if (typeof queryOrAST === 'string') {
+    queryAST = { text: queryOrAST, filters }
+  } else {
+    queryAST = queryOrAST
+  }
+
+  const { text: queryText, filters: appliedFilters } = queryAST
+  const queryLower = queryText.toLowerCase().trim()
 
   const allNotes = await prisma.note.findMany({
     include: { tags: { include: { tag: true } } },
@@ -145,12 +157,14 @@ export async function noteQuery(
   const scored: ScoredNote[] = []
 
   for (const note of allNotes) {
-    if (filters.type && note.type !== filters.type) continue
-
-    if (filters.tag) {
-      const hasTag = note.tags.some(t => t.tag.name === filters.tag)
+    // Apply filters from AST BEFORE scoring
+    if (appliedFilters.type && note.type !== appliedFilters.type) continue
+    if (appliedFilters.tag) {
+      const hasTag = note.tags.some(t => t.tag.name === appliedFilters.tag)
       if (!hasTag) continue
     }
+    if (appliedFilters.isFavorite && note.isFavorite !== true) continue
+    if (appliedFilters.isPinned && note.isPinned !== true) continue
 
     const titleLower = note.title.toLowerCase()
     const contentLower = note.content.toLowerCase()
@@ -181,7 +195,7 @@ export async function noteQuery(
 
     const highlight = highlightMatches(
       exactTitleMatch ? note.title + ' ' + note.content : note.content,
-      query
+      queryText
     )
 
     scored.push({
@@ -202,5 +216,11 @@ export async function searchNotes(
   query: string,
   filters: SearchFilters = {}
 ): Promise<ScoredNote[]> {
-  return noteQuery(query, filters)
+  const queryAST: QueryAST = {
+    text: query,
+    filters: {
+      ...filters,
+    },
+  }
+  return noteQuery(queryAST)
 }