fix(acr): enumerateAgents counts only CC-registered agents — recurse + frontmatter filter + HOME dedup (M-BUG-3/4/5)

enumerateAgents previously counted every .md in an agents dir as an
always-loaded agent. Per the official CC subagents docs, CC registers a
subagent only when its frontmatter declares both name and description, scans
agents dirs recursively, and (at a HOME self-scan) must not count
~/.claude/agents twice.

- M-BUG-5: require valid name+description frontmatter; frontmatter-less files
  are registration no-ops costing 0 always-loaded tokens. Fixes the user-agent
  over-count (this machine: 13 -> 0).
- M-BUG-3: listMarkdownFiles gains opt-in recursion; enumerateAgents recurses
  so agents in subfolders (agents/review/x.md) are counted, matching CC.
- M-BUG-4: configDirs dedupes project==user paths, so a `manifest --global`
  self-scan (repoPath===$HOME) counts ~/.claude once (user scope), killing the
  spurious "project 13" double-count. Benefits rules/agents/output-styles.

TDD: 4 failing tests -> green. Full suite 1305/0; --json/--raw byte-stable,
frozen v5.0.0 + SC-5 + default-output snapshots untouched (no snapshot records
agent enumeration rows).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EnUvKEqyEa1m9gy6Aqhdqq

tests/lib/active-config-reader.test.mjs

@@ -952,6 +952,70 @@ describe('enumerateAgents (v5.6)', () => {
     await mkdir(root, { recursive: true });
     assert.deepEqual(await enumerateAgents(root, []), []);
   });
+
+  // M-BUG-5: CC registers a subagent only when its frontmatter declares both
+  // `name` and `description` (docs: identity comes only from `name`; both are
+  // required). Frontmatter-less / incomplete files are registration no-ops that
+  // cost zero always-loaded tokens — they must NOT be counted as agents.
+  it('M-BUG-5: skips files with no frontmatter at all', async () => {
+    const dir = join(root, '.claude', 'agents');
+    await mkdir(dir, { recursive: true });
+    await writeFile(join(dir, 'reviewer.md'), '---\nname: reviewer\ndescription: reviews code\n---\nbody\n');
+    await writeFile(join(dir, 'not-an-agent.md'), '# Not An Agent\n\nJust a markdown doc, no frontmatter.\n');
+    const agents = await enumerateAgents(root, []);
+    assert.deepEqual(agents.map(a => a.name).sort(), ['reviewer']);
+  });
+
+  it('M-BUG-5: skips files missing name or description', async () => {
+    const dir = join(root, '.claude', 'agents');
+    await mkdir(dir, { recursive: true });
+    await writeFile(join(dir, 'reviewer.md'), '---\nname: reviewer\ndescription: reviews code\n---\nbody\n');
+    await writeFile(join(dir, 'name-only.md'), '---\nname: name-only\n---\nbody\n');
+    await writeFile(join(dir, 'desc-only.md'), '---\ndescription: has no name\n---\nbody\n');
+    await writeFile(join(dir, 'empty-name.md'), '---\nname:\ndescription: blank name\n---\nbody\n');
+    const agents = await enumerateAgents(root, []);
+    assert.deepEqual(agents.map(a => a.name).sort(), ['reviewer']);
+  });
+
+  // M-BUG-3: CC scans agents dirs recursively, so a valid agent in a subfolder
+  // (e.g. agents/review/security.md) is registered and must be counted.
+  it('M-BUG-3: recurses into agent subdirectories', async () => {
+    const sub = join(root, '.claude', 'agents', 'review');
+    await mkdir(sub, { recursive: true });
+    await writeFile(join(sub, 'security.md'), '---\nname: security\ndescription: security review\n---\nbody\n');
+    const agents = await enumerateAgents(root, []);
+    const a = agents.find(x => x.name === 'security');
+    assert.ok(a, 'agent in subdir should be counted');
+    assert.equal(a.source, 'project');
+  });
+});
+
+// M-BUG-4: when repoPath === $HOME (the `manifest --global` self-scan), the
+// project agents dir resolves to the SAME path as the user agents dir. The
+// shared configDirs helper must count it once (as user scope), not twice.
+describe('enumerateAgents — HOME self-scan dedup (M-BUG-4)', () => {
+  let home, originalHome;
+  beforeEach(async () => {
+    home = uniqueDir('agents-home-selfscan');
+    await mkdir(join(home, '.claude', 'agents'), { recursive: true });
+    originalHome = process.env.HOME;
+    process.env.HOME = home;
+  });
+  afterEach(async () => {
+    process.env.HOME = originalHome;
+    await rm(home, { recursive: true, force: true });
+  });
+
+  it('does not double-count user agents when repoPath === HOME', async () => {
+    await writeFile(
+      join(home, '.claude', 'agents', 'solo.md'),
+      '---\nname: solo\ndescription: only one of me\n---\nbody\n',
+    );
+    const agents = await enumerateAgents(home, []);
+    const solos = agents.filter(a => a.name === 'solo');
+    assert.equal(solos.length, 1, 'agent at HOME must be counted once, not twice');
+    assert.equal(solos[0].source, 'user', 'HOME self-scan agents are user scope');
+  });
 });
 
 describe('enumerateOutputStyles (v5.6)', () => {