build: discover owned runtime modules in the formatter gate

scripts/format-runtime.json

@@ -0,0 +1,3 @@
+{
+  "roots": ["src", "server"]
+}

scripts/format-scope.json

@@ -722,5 +722,6 @@
   "scripts/qa-transit-scenes.mjs",
   "scripts/qa-transit-controls.mjs",
   "src/tooling/transitQa.test.mjs",
-  "scripts/qa-transit-browser.mjs"
+  "scripts/qa-transit-browser.mjs",
+  "scripts/format-runtime.json"
 ]

scripts/format.mjs

@@ -1,9 +1,58 @@
+import { execFileSync } from 'node:child_process';
+import { existsSync } from 'node:fs';
 import { readFile, writeFile, realpath, stat } from 'node:fs/promises';
 import path from 'node:path';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 import * as prettier from 'prettier';
 
-/** Check or format the explicitly adopted files, without scanning other source. */
+/** Discover owned runtime code; tests and other files retain explicit adoption. */
+export async function discoverRuntimeFormatFiles(root) {
+  const configFile = path.join(root, 'scripts/format-runtime.json');
+  if (!existsSync(configFile)) return [];
+  const { roots } = JSON.parse(await readFile(configFile, 'utf8'));
+  if (
+    !Array.isArray(roots) ||
+    !roots.length ||
+    new Set(roots).size !== roots.length ||
+    roots.some(
+      (name) =>
+        typeof name !== 'string' ||
+        !/^[a-zA-Z0-9_-]+(?:\/[a-zA-Z0-9_-]+)*$/.test(name),
+    )
+  )
+    throw new Error(
+      'Runtime formatting roots must be unique repository directory paths',
+    );
+  const candidates = execFileSync(
+    'git',
+    [
+      'ls-files',
+      '-z',
+      '--cached',
+      '--others',
+      '--exclude-standard',
+      '--',
+      ...roots,
+    ],
+    { cwd: root, encoding: 'utf8' },
+  ).split('\0');
+  const files = [];
+  for (const name of new Set(candidates)) {
+    if (
+      !/\.[cm]?js$/.test(name) ||
+      /\.test\.[cm]?js$/.test(name) ||
+      !existsSync(path.join(root, name))
+    )
+      continue;
+    const info = await prettier.getFileInfo(path.join(root, name), {
+      ignorePath: path.join(root, '.prettierignore'),
+    });
+    if (!info.ignored) files.push(name);
+  }
+  return files.sort();
+}
+
+/** Check or format explicit adoption plus automatically discovered runtime code. */
 export async function formatAdoptedFiles(root, mode) {
   if (!['--check', '--write'].includes(mode)) {
     throw new Error('Usage: node scripts/format.mjs --check|--write');
@@ -22,9 +71,13 @@ export async function formatAdoptedFiles(root, mode) {
     );
   }
 
+  const names = [
+    ...new Set([...scope, ...(await discoverRuntimeFormatFiles(root))]),
+  ];
+
   // Validate the whole scope before any write, including resolved symlink paths.
   const files = [];
-  for (const name of scope) {
+  for (const name of names) {
     if (
       typeof name !== 'string' ||
       !name ||
@@ -91,7 +144,7 @@ if (import.meta.url === invoked) {
       process.exitCode = 1;
     } else {
       console.log(
-        `${mode === '--write' ? 'Formatted' : 'Checked'} ${result.count} adopted files.`,
+        `${mode === '--write' ? 'Formatted' : 'Checked'} ${result.count} source files.`,
       );
     }
   } catch (error) {