fix(db): strip ; from -- comment + add regression guard

CI failed again with the same `RangeError: The supplied SQL string
contains no statements` from yesterday's lesson — I introduced a `;`
inside the freshly-rewritten recipe_recency DDL block comment when
applying CodeRabbit nitpick #2 (the lazy-on-read prose fix).

Two changes:

1. Replaced "(recordRecipeRun DELETEs stale rows before its upsert);
   reads stay pure." with em-dash to drop the inner `;`. (Same fix
   shape as 649f7d2 from the previous round.)

2. **Added a regression guard** in `src/db.test.ts` that splits the
   `createTables()` template on `;` and asserts no fragment is pure
   `--` comments. Hitting this lesson twice in one PR is the trigger
   the existing entry in `.agents/lessons.md` flagged as "candidate
   roadmap item." Test runs in `bun test` (which Bun's `bun:sqlite`
   masks), so it catches the regression locally before CI burns a
   cycle.

887 → 888 tests; CI's `node dist/index.mjs --full` smoke verified
locally before push.

Author: SutuSebastian

src/db.test.ts

@@ -1,4 +1,6 @@
 import { describe, expect, it } from "bun:test";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
 
 import {
   closeDb,
@@ -18,6 +20,35 @@ import {
 } from "./db";
 import { openCodemapDatabase } from "./sqlite-db";
 
+describe("createTables() DDL — Node split-on-`;` invariant", () => {
+  // Node uses better-sqlite3 (one statement per `prepare()`), so `runSql()`
+  // splits the multi-statement DDL on `;`. A `;` inside a `--` line comment
+  // creates a comment-only fragment that `prepare()` rejects with
+  // `RangeError: The supplied SQL string contains no statements`. Bun tests
+  // miss this because `bun:sqlite` accepts multi-statement SQL natively;
+  // the failure surfaces only when CI runs `node dist/index.mjs --full`.
+  // See `.agents/lessons.md` "Semicolons inside `--` line comments".
+  it("contains no comment-only fragments after split-on-`;`", () => {
+    const src = readFileSync(join(import.meta.dir, "db.ts"), "utf-8");
+    const match = src.match(/createTables[^`]*`([\s\S]+?)`/);
+    expect(match).not.toBeNull();
+    const sql = match![1]!;
+    const fragments = sql
+      .split(";")
+      .map((s) => s.trim())
+      .filter(Boolean);
+    const offenders = fragments.filter((f) => {
+      const stripped = f
+        .split("\n")
+        .map((l) => l.trim())
+        .filter((l) => l && !l.startsWith("--"))
+        .join(" ");
+      return stripped === "";
+    });
+    expect(offenders).toEqual([]);
+  });
+});
+
 describe("SQLite layer (in-memory)", () => {
   it("creates schema and round-trips meta", () => {
     const db = openCodemapDatabase(":memory:");

src/db.ts

@@ -199,8 +199,8 @@ export function createTables(db: CodemapDatabase) {
     -- loadRecipeRecency. Like query_baselines / coverage, intentionally absent
     -- from dropAll() so --full and SCHEMA_VERSION rebuilds preserve activity
     -- history. 90-day window is eager-on-write (recordRecipeRun DELETEs stale
-    -- rows before its upsert); reads stay pure. recipe_id is loose (no FK; can
-    -- match bundled or project recipe ids). See docs/architecture.md recipe_recency.
+    -- rows before its upsert) — reads stay pure. recipe_id is loose (no FK,
+    -- can match bundled or project recipe ids). See docs/architecture.md.
     CREATE TABLE IF NOT EXISTS recipe_recency (
       recipe_id   TEXT PRIMARY KEY,
       last_run_at INTEGER NOT NULL,