chore(template): clean-slate template snapshot from bb4a0c7

Curated, product-agnostic snapshot of the post-story-04 tree: demo
content deleted, auth-only reference feature, web-next shell, all gates
green. Product-specific docs, ADRs 027-029, PRDs/epics/archive, editor
library traces, and product naming are curated out; generic template
repairs (coverage provider devDeps, root test:coverage script, live
lint fixes, root-only release-please) are kept. See TEMPLATE.md for
provenance, curation list, and usage.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016j8z4VHjedXDTjEDNg7qHK

scripts/coverage/mutate.mjs

@@ -0,0 +1,158 @@
+#!/usr/bin/env node
+// scripts/coverage/mutate.mjs — L3 of the coverage architecture (ADR-020).
+//
+// Driver for Stryker mutation testing. Discovers every package with a
+// stryker.config.json, then runs Stryker per-feature with the feature's
+// vitest config + a narrowed mutate scope (entities + use-cases by default,
+// per the shared base config).
+//
+// Usage:
+//   pnpm mutate                            # run for every feature with a config
+//   pnpm mutate -- --filter @repo/auth     # run for one feature
+//   pnpm mutate -- --filter @repo/auth --since main  # incremental mode
+//   pnpm mutate -- --json                  # machine-readable summary only
+//
+// This runs Stryker as a child process, not via dynamic import — Stryker's
+// runtime expects to own the test process and our wrapping logic keeps the
+// integration simple. Stryker handles concurrency internally.
+
+import fs from "node:fs";
+import path from "node:path";
+import { spawnSync } from "node:child_process";
+
+const STRYKER_BIN = "node_modules/.bin/stryker";
+
+/**
+ * Walk packages/* and apps/* for stryker.config.json files.
+ * Returns: [{ packageDir, packageName, configPath }]
+ */
+export function discoverStrykerConfigs(repoRoot) {
+  const out = [];
+  for (const root of ["packages", "apps"]) {
+    const dir = path.join(repoRoot, root);
+    if (!fs.existsSync(dir)) continue;
+    for (const pkg of fs.readdirSync(dir)) {
+      const configPath = path.join(dir, pkg, "stryker.config.json");
+      if (!fs.existsSync(configPath)) continue;
+      const pkgJsonPath = path.join(dir, pkg, "package.json");
+      let packageName = `${root}/${pkg}`;
+      if (fs.existsSync(pkgJsonPath)) {
+        try {
+          packageName =
+            JSON.parse(fs.readFileSync(pkgJsonPath, "utf8")).name ??
+            packageName;
+        } catch {
+          // fall through
+        }
+      }
+      out.push({
+        packageDir: path.join(root, pkg),
+        packageName,
+        configPath,
+      });
+    }
+  }
+  return out.sort((a, b) => a.packageDir.localeCompare(b.packageDir));
+}
+
+function parseArgs(argv) {
+  const out = { filter: null, since: null, json: false };
+  for (let i = 2; i < argv.length; i++) {
+    const a = argv[i];
+    if (a === "--filter") out.filter = argv[++i];
+    else if (a === "--since") out.since = argv[++i];
+    else if (a === "--json") out.json = true;
+    else if (a === "--help" || a === "-h") {
+      console.log(
+        "Usage: pnpm mutate [-- --filter <name>] [--since <ref>] [--json]",
+      );
+      process.exit(0);
+    }
+  }
+  return out;
+}
+
+function main() {
+  const args = parseArgs(process.argv);
+  const repoRoot = process.cwd();
+  const all = discoverStrykerConfigs(repoRoot);
+
+  const targets = args.filter
+    ? all.filter(
+        (c) =>
+          c.packageName === args.filter || c.packageDir.endsWith(args.filter),
+      )
+    : all;
+
+  if (targets.length === 0) {
+    process.stderr.write(
+      `[mutate] No stryker.config.json found${args.filter ? ` matching ${args.filter}` : ""}.\n` +
+        `Each feature wanting L3 mutation needs a stryker.config.json. See docs/guides/coverage.md.\n`,
+    );
+    process.exit(args.filter ? 1 : 0);
+  }
+
+  const strykerBinAbs = path.join(repoRoot, STRYKER_BIN);
+  if (!fs.existsSync(strykerBinAbs)) {
+    process.stderr.write(
+      `[mutate] Stryker binary not found at ${STRYKER_BIN}. Run \`pnpm install\`.\n`,
+    );
+    process.exit(1);
+  }
+
+  const results = [];
+  for (const target of targets) {
+    if (!args.json) {
+      process.stderr.write(
+        `\n[mutate] === ${target.packageName} (${target.packageDir}) ===\n`,
+      );
+    }
+
+    const strykerArgs = ["run", target.configPath];
+    if (args.since) {
+      strykerArgs.push("--since", args.since);
+    }
+
+    const result = spawnSync(strykerBinAbs, strykerArgs, {
+      cwd: path.join(repoRoot, target.packageDir),
+      stdio: args.json ? "pipe" : "inherit",
+      env: { ...process.env, FORCE_COLOR: args.json ? "0" : "1" },
+    });
+
+    results.push({
+      package: target.packageName,
+      packageDir: target.packageDir,
+      exitCode: result.status,
+      status: result.status === 0 ? "pass" : "fail",
+    });
+
+    // If a feature fails, continue to next. Surface failures at the end so
+    // a single broken feature doesn't mask state for the others.
+  }
+
+  const anyFailed = results.some((r) => r.exitCode !== 0);
+
+  if (args.json) {
+    process.stdout.write(
+      JSON.stringify(
+        { status: anyFailed ? "fail" : "pass", results },
+        null,
+        2,
+      ) + "\n",
+    );
+  } else {
+    process.stderr.write("\n[mutate] Summary:\n");
+    for (const r of results) {
+      process.stderr.write(
+        `  ${r.status === "pass" ? "✓" : "✗"} ${r.package}\n`,
+      );
+    }
+  }
+
+  process.exit(anyFailed ? 1 : 0);
+}
+
+const invokedDirectly = import.meta.url === `file://${process.argv[1]}`;
+if (invokedDirectly) {
+  main();
+}