Discover test suites instead of listing them by hand

Both package.json files carried the suite list on one line — `node a.test.mjs &&
node b.test.mjs && …` — so every PR that added a test edited the same line and
any two of them conflicted by construction; six times in the last few days. The
damage is not the conflict, it is the resolution: taking one side drops the
other PR's suite from the run, CI stays green, and the missing coverage is
invisible. `npm test` in each package now discovers what to run.

The rule is `test/*.test.mjs`, then `*.test.mjs` at the package root,
alphabetically within each. A suite that must stay out of the default set says
so in its own header — a line containing `am-test: manual` and the reason — and
every run prints what it skipped and why, so nothing goes quiet again. That
covers the five that were already excluded by omission: the four server suites
needing Chromium and a full web build (terminal-ui, screenshot-input,
reader-info, mobile) and web's statusMark.render, which keep their own scripts.

Sequential, deliberately. `node --test` would discover the same files but runs
them in parallel, and suites here bind fixed ports (migration 7893, resize 7895,
trace-download 7898) and drive Chromium. Those ports are distinct today only
because whoever added each picked a free number; nothing enforces it, and the
first suite that copies an existing PORT constant would produce a flake that
reads as a product bug. The runner spawns one child at a time and stops at the
first failure with its exit code, which is what the `&&` chain did.

Two server suites start running that never had: test/backup.test.mjs and
test/backup-health.test.mjs, added with the bucket-backup work (#26, #34) and
never referenced by any script. They are node:test files, they pass, they take
45ms between them, and they touch no ports — 33 assertions that were being
carried but not run.

scripts/run-suites.mjs

@@ -0,0 +1,94 @@
+// Runs a package's test suites: every `*.test.mjs` in `test/`, then every one at
+// the package root, in that order, one at a time.
+//
+// WHY THIS EXISTS. Both package.json files used to carry the suite list by hand
+// —  `node a.test.mjs && node b.test.mjs && …` on one line. Every PR that added
+// a test edited that line, so any two such PRs conflicted by construction (six
+// times in the last few days), and the natural resolution — take one side —
+// silently drops the other PR's suite from the run. It stays green and nobody
+// notices the coverage is gone. Discovery removes the shared line: adding
+// `test/foo.test.mjs` is enough to make it run.
+//
+// SEQUENTIAL, DELIBERATELY. `node --test` would also discover these files, but
+// it runs them in PARALLEL by default, and several suites here start a real
+// server on a fixed port (migration on 7893, resize on 7895, trace-download on
+// 7898) or drive Chromium. Those ports do not collide today, but only because
+// whoever added each one picked a free number — nothing enforces it, and the
+// first suite that copies an existing PORT constant produces a flake that reads
+// as a product bug. This fleet has already lost time to exactly that symptom.
+// One at a time costs wall-clock and nothing else.
+//
+// EXIT SEMANTICS match the `&&` chain it replaces: the first failing suite stops
+// the run and its exit code is this process's exit code. That holds for both
+// kinds of file here — the standalone scripts that print their own results and
+// call process.exit, and the two `node:test` suites, which node exits non-zero
+// for when a test fails (verified, not assumed).
+//
+// OPTING OUT. A suite that must not run in the default set says so in its own
+// header, on a line containing `am-test: manual` plus the reason. It is declared
+// where a reader will see it rather than by absence from a list somewhere else,
+// and every run prints what it skipped and why, so coverage cannot go quiet.
+//
+// Usage:  node ../scripts/run-suites.mjs [substring …]
+//         (a substring filters to matching suites — for running one by hand)
+import fs from 'node:fs';
+import path from 'node:path';
+import { spawnSync } from 'node:child_process';
+
+const MANUAL = /am-test:\s*manual\s*[—:-]?\s*(.*)/;
+const HEAD_BYTES = 4096;          // the marker belongs in the header, not line 900
+
+const listDir = (dir) => {
+  let names = [];
+  try { names = fs.readdirSync(dir); } catch { return []; }
+  return names
+    .filter((n) => n.endsWith('.test.mjs'))
+    .sort((a, b) => a.localeCompare(b, 'en'))
+    .map((n) => path.join(dir, n))
+    .filter((p) => fs.statSync(p).isFile());
+};
+
+// `test/` first, then the package root: the root files are the older ones, and
+// keeping them behind the directory keeps the common case (a new suite in
+// test/) at the front of the run.
+const found = [...listDir('test'), ...listDir('.')];
+
+const filters = process.argv.slice(2);
+const suites = [];
+const skipped = [];
+for (const file of found) {
+  let head = '';
+  try {
+    const fd = fs.openSync(file, 'r');
+    const buf = Buffer.alloc(HEAD_BYTES);
+    head = buf.subarray(0, fs.readSync(fd, buf, 0, HEAD_BYTES, 0)).toString('utf8');
+    fs.closeSync(fd);
+  } catch { /* unreadable: let node report it */ }
+  const manual = head.match(MANUAL);
+  if (manual) { skipped.push({ file, why: manual[1].trim() }); continue; }
+  if (filters.length && !filters.some((f) => file.includes(f))) continue;
+  suites.push(file);
+}
+
+const pkg = path.basename(process.cwd());
+if (!suites.length) {
+  console.error(`no suites found in ${pkg}/${filters.length ? ` matching ${filters.join(', ')}` : ''}`);
+  process.exit(1);
+}
+const plural = (n) => `${n} suite${n === 1 ? '' : 's'}`;
+console.log(`${pkg}: ${plural(suites.length)}\n`);
+
+for (const [i, file] of suites.entries()) {
+  console.log(`── [${i + 1}/${suites.length}] ${file}`);
+  const r = spawnSync(process.execPath, [file], { stdio: 'inherit' });
+  const code = r.status === null ? 1 : r.status;
+  if (code !== 0) {
+    console.error(`\n${file} FAILED (${r.signal ? `signal ${r.signal}` : `exit ${code}`})`);
+    console.error(`${plural(i)} had passed before it; the rest were not started.`);
+    process.exit(code);
+  }
+  console.log('');
+}
+
+console.log(`${pkg}: ${plural(suites.length)} passed`);
+for (const { file, why } of skipped) console.log(`  skipped ${file} — ${why || 'marked manual'}`);

server/mobile.test.mjs

@@ -5,6 +5,7 @@
 // visual viewport is replaced with a controllable EventTarget so the keyboard
 // test covers both viewport height and iOS's non-zero offsetTop.
 //
+// am-test: manual — Chromium, a full web build and port 7896; `npm run test:mobile`.
 //   npm run test:mobile
 import fs from 'node:fs';
 import os from 'node:os';

server/package.json

@@ -16,7 +16,7 @@
     "test:ui": "node terminal-ui.test.mjs && node screenshot-input.test.mjs && node reader-info.test.mjs",
     "test:screenshots": "node screenshot-input.test.mjs",
     "test:mobile": "node mobile.test.mjs",
-    "test": "node test/archive.test.mjs && node test/trace-download.test.mjs && node test/attachments.test.mjs && node state-checkpoint.test.mjs && node test/usage.test.mjs && node test/operations.test.mjs && node test/hidden.test.mjs && node test/slowfs.test.mjs && node test/spawn-group.test.mjs && node test/revive.test.mjs && node test/repin.test.mjs && node test/codex-repin.test.mjs && node test/opencode-resume.test.mjs && node test/input-required.test.mjs && node test/terminal-modes.test.mjs && node test/trace-tail.test.mjs && node test/trace-window.test.mjs && node migration.test.mjs && node resize.test.mjs"
+    "test": "node ../scripts/run-suites.mjs"
   },
   "engines": {
     "node": ">=20.19"

server/reader-info.test.mjs

@@ -11,6 +11,7 @@
  *
  * Set READER_INFO_PUBLIC_DIR to a prebuilt web/dist to skip the build, and
  * READER_INFO_PORT to move off the default when suites run in parallel.
+ * am-test: manual — Chromium, a full web build and READER_INFO_PORT; `npm run test:ui`.
  */
 import fs from 'node:fs';
 import os from 'node:os';

server/screenshot-input.test.mjs

@@ -12,6 +12,7 @@
  *   - the creation dialog has no redundant file picker.
  *
  * Set SCREENSHOT_PUBLIC_DIR to a prebuilt web/dist to skip the build.
+ * am-test: manual — Chromium, a full web build and SCREENSHOT_PORT; `npm run test:ui`.
  */
 import fs from 'node:fs';
 import os from 'node:os';

server/terminal-ui.test.mjs

@@ -7,6 +7,7 @@
  *   - ...without letting that lingering selection shadow Ctrl+C's SIGINT
  *
  * Set TERMUI_PUBLIC_DIR to a prebuilt web/dist to skip the build.
+ * am-test: manual — Chromium, a full web build and port 7897; `npm run test:ui`.
  */
 import fs from 'node:fs';
 import os from 'node:os';

web/package.json

@@ -13,7 +13,7 @@
     "dev": "vite",
     "build": "tsc --noEmit && vite build",
     "typecheck": "tsc --noEmit",
-    "test": "node test/stepMarkdown.test.mjs && node test/statusMark.test.mjs && node test/mobileBack.test.mjs && node test/pendingExchange.test.mjs && node test/composerAlign.test.mjs && node test/fileWrapToggle.test.mjs && node test/exchanges.test.mjs && node test/sessionTitle.test.mjs && node test/overviewSort.test.mjs && node test/drafts.test.mjs && node test/settingsMobile.test.mjs && node test/traceWindows.test.mjs && node test/sidebar-dnd.test.mjs",
+    "test": "node ../scripts/run-suites.mjs",
     "test:render": "node test/statusMark.render.test.mjs",
     "preview": "vite preview"
   },

web/test/statusMark.render.test.mjs

@@ -6,8 +6,10 @@
 // mark, and a state pseudo-element never paints over the inline provider/CLI
 // colours carried by bare `.status` dots.
 //
-// Needs Chromium; run with:  node test/statusMark.render.test.mjs
-// (not in `npm test`, which stays browser-free — see package.json's test:render)
+// am-test: manual — needs Chromium; run with `npm run test:render`.
+// Kept out of the default suite as its own script, unchanged by the discovery
+// change. (The note that used to sit here said `npm test` stays browser-free;
+// that stopped being true when traceWindows.test.mjs joined it.)
 import assert from 'node:assert/strict';
 import fs from 'node:fs';
 import path from 'node:path';