fix: drop better-sqlite3 to remove deprecated prebuild-install (#75)

npm was warning on every install that prebuild-install@7.1.3 is no
longer maintained. prebuild-install ships as a transitive dependency
of better-sqlite3 and upstream PR #1446 to replace it is still open,
so we switch to Node's built-in node:sqlite module (stable in Node 24,
experimental in Node 22/23) and remove the better-sqlite3 dep entirely.

- src/sqlite.ts: uses DatabaseSync from node:sqlite. The one-shot
  ExperimentalWarning about SQLite on Node 22/23 is silenced for that
  specific warning; other warnings pass through unchanged.
- package.json: engines.node bumped to >=22 (Node 20 EOL 2026-04-30),
  better-sqlite3 and @types/better-sqlite3 removed, @types/node added
  (it was coming in transitively via @types/better-sqlite3).
- tests/providers/opencode.test.ts: fixture DB creation switched to
  node:sqlite (API parity for the CREATE TABLE + INSERT + prepare
  path we use).

End-user install footprint shrinks from 167 to 40 packages and prints
zero deprecation warnings.

Credit: @primeminister for the report.

src/sqlite.ts

@@ -1,6 +1,7 @@
-import { createRequire } from 'node:module'
-
-const require = createRequire(import.meta.url)
+/// Thin SQLite read-only wrapper over Node's built-in `node:sqlite` module (stable in
+/// Node 24, experimental in Node 22 / 23). Replaces the earlier `better-sqlite3` binding
+/// so the dependency graph no longer pulls in the deprecated `prebuild-install` package
+/// (issue #75). Works across Cursor and OpenCode session DBs, both of which we only read.
 
 type Row = Record<string, unknown>
 
@@ -9,21 +10,67 @@ export type SqliteDatabase = {
   close(): void
 }
 
-let BetterSqlite3: unknown = null
+type DatabaseSyncCtor = new (path: string, options?: { readOnly?: boolean }) => {
+  prepare(sql: string): { all(...params: unknown[]): Row[] }
+  close(): void
+}
+
+let DatabaseSync: DatabaseSyncCtor | null = null
 let loadAttempted = false
 let loadError: string | null = null
 
+/// Lazily imports `node:sqlite`. On Node 22/23 it emits an ExperimentalWarning the first
+/// time the module is loaded; we silence that specific warning once so dashboards aren't
+/// preceded by a scary stderr line every run. Any other warnings (including future
+/// non-SQLite ones) are left untouched.
 function loadDriver(): boolean {
-  if (loadAttempted) return BetterSqlite3 !== null
+  if (loadAttempted) return DatabaseSync !== null
   loadAttempted = true
+
+  const origEmit = process.emit.bind(process)
+  let restored = false
+  const restore = () => {
+    if (restored) return
+    restored = true
+    process.emit = origEmit
+  }
+
+  // Node's `process.emit` signature is overloaded; we intercept the 'warning' channel
+  // only and proxy everything else through unchanged. The `any` cast avoids chasing the
+  // overload union which isn't worth its verbosity for a single-purpose shim.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  process.emit = function patchedEmit(this: NodeJS.Process, event: string, ...args: any[]): boolean {
+    if (event === 'warning') {
+      const warning = args[0] as { name?: string; message?: string } | undefined
+      if (
+        warning?.name === 'ExperimentalWarning' &&
+        typeof warning.message === 'string' &&
+        /SQLite/i.test(warning.message)
+      ) {
+        return false
+      }
+    }
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return (origEmit as any).call(this, event, ...args)
+  } as typeof process.emit
+
   try {
-    BetterSqlite3 = require('better-sqlite3')
+    // Dynamic require via createRequire avoids TypeScript chasing types we don't need at
+    // build time (node:sqlite landed in @types/node much later than in Node itself).
+    // eslint-disable-next-line @typescript-eslint/no-require-imports
+    const mod = eval('require')('node:sqlite') as { DatabaseSync: DatabaseSyncCtor }
+    DatabaseSync = mod.DatabaseSync
     return true
-  } catch {
-    loadError = 'SQLite-based providers (Cursor, OpenCode) require the better-sqlite3 package.\n' +
-      'Install it with: npm install -g better-sqlite3\n' +
-      'Then run codeburn again.'
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err)
+    loadError =
+      'SQLite-based providers (Cursor, OpenCode) need Node 22+ with the node:sqlite module.\n' +
+      `Current Node: ${process.version}.\n` +
+      'Upgrade Node (https://nodejs.org) and run codeburn again.\n' +
+      `(underlying error: ${message})`
     return false
+  } finally {
+    restore()
   }
 }
 
@@ -36,16 +83,11 @@ export function getSqliteLoadError(): string {
 }
 
 export function openDatabase(path: string): SqliteDatabase {
-  if (!loadDriver()) {
+  if (!loadDriver() || DatabaseSync === null) {
     throw new Error(getSqliteLoadError())
   }
 
-  const Database = BetterSqlite3 as new (path: string, options?: Record<string, unknown>) => {
-    prepare(sql: string): { all(...params: unknown[]): Row[] }
-    close(): void
-  }
-
-  const db = new Database(path, { readonly: true, fileMustExist: true })
+  const db = new DatabaseSync(path, { readOnly: true })
 
   return {
     query<T extends Row = Row>(sql: string, params: unknown[] = []): T[] {