test(webapp): guard against a raw-SQL reference to the dropped chats.messages

The transcript moved out of `chats.messages` into `chat_messages`. TypeScript
already rejects a reference through the Drizzle schema, but a raw-SQL reference
compiles fine and only fails at runtime, and the earlier guard test went away
with the column. Zero hits today is the point: the test exists so a
reintroduction is caught rather than deployed.

Author: kathiekiwi

apps/webapp/test/dashboardAgentLegacyMessagesColumn.test.ts

@@ -0,0 +1,75 @@
+import { readdirSync, readFileSync, statSync } from "node:fs";
+import path from "node:path";
+import { describe, expect, it } from "vitest";
+
+/**
+ * `chats.messages` is gone: the transcript lives in `chat_messages`, one row per message.
+ *
+ * TypeScript already catches a reference through the Drizzle schema — the column isn't
+ * there, so it doesn't compile. A raw-SQL reference compiles fine and fails at runtime,
+ * which is the hole this scan covers. Zero hits today is the point; the test exists so a
+ * reintroduction is caught rather than deployed.
+ */
+
+const ROOT = path.resolve(__dirname, "../../..");
+
+const SCANNED = [
+  "apps/webapp/app",
+  "internal-packages/dashboard-agent/src",
+  "internal-packages/dashboard-agent-db/src",
+];
+
+/** A qualified reference to the dropped column, in any of the spellings Postgres accepts. */
+const QUALIFIED = /"?\bchats"?\s*\.\s*"?messages"?/i;
+
+/** An unqualified one, inside a literal that is plainly SQL against `chats`. */
+const SQL_LITERAL = /`[^`]*`|"(?:[^"\\\n]|\\.)*"|'(?:[^'\\\n]|\\.)*'/g;
+const SQL_VERB = /\b(select|insert\s+into|update|delete\s+from)\b/i;
+const NAMES_CHATS = /(?<![\w."])chats\b/i;
+// Word-boundary on both sides and no leading `_`, so `chat_messages` is not a hit.
+const BARE_MESSAGES = /(?<![\w."])messages\b/i;
+
+function sourceFiles(dir: string): string[] {
+  const found: string[] = [];
+  for (const entry of readdirSync(dir)) {
+    const full = path.join(dir, entry);
+    if (statSync(full).isDirectory()) {
+      if (entry === "node_modules" || entry === "drizzle") continue;
+      found.push(...sourceFiles(full));
+      continue;
+    }
+    if (!/\.(ts|tsx)$/.test(entry)) continue;
+    // Tests are excluded: they are allowed to name the old column to describe it.
+    if (/\.(test|eval|spec)\.tsx?$/.test(entry)) continue;
+    found.push(full);
+  }
+  return found;
+}
+
+function offences(file: string): string[] {
+  const text = readFileSync(file, "utf8");
+  const found: string[] = [];
+
+  for (const [index, line] of text.split("\n").entries()) {
+    if (QUALIFIED.test(line))
+      found.push(`${path.relative(ROOT, file)}:${index + 1} ${line.trim()}`);
+  }
+
+  for (const literal of text.match(SQL_LITERAL) ?? []) {
+    if (!SQL_VERB.test(literal) || !NAMES_CHATS.test(literal)) continue;
+    if (!BARE_MESSAGES.test(literal)) continue;
+    found.push(`${path.relative(ROOT, file)} (sql literal) ${literal.slice(0, 120)}`);
+  }
+
+  return found;
+}
+
+describe("the dropped chats.messages column", () => {
+  it("is not referenced by any production source, including in raw SQL", () => {
+    const files = SCANNED.flatMap((dir) => sourceFiles(path.join(ROOT, dir)));
+    // A scan that found nothing to read would pass vacuously.
+    expect(files.length).toBeGreaterThan(200);
+
+    expect(files.flatMap(offences)).toEqual([]);
+  });
+});