fix(hermes): preserve YAML list-at-same-indent style on install (#456) (#461)

Hermes Agent writes ~/.hermes/config.yaml with PyYAML's default block
style, which puts list items at the SAME indent as the parent key:

    platform_toolsets:
      cli:
      - hermes-cli      # indent 2, same as `cli:`
      - browser

The previous line-based YAML patcher used `^  \S` to find the end of
the `cli:` block, which mistook that first `  - hermes-cli` line for
the next sibling key, truncated the block, and spliced
`    - mcp-codegraph` at indent 4 BEFORE the existing items. The
result was unparseable YAML: every subsequent item (`- browser`,
`- clarify`, …) and every sibling platform (`telegram:`, `discord:`)
appeared at the `platform_toolsets:` level. Hermes silently fell back
to the default config, dropping every user override.

The new `listChildBlock` helper recognizes `  - ` as a list-item
continuation (not a sibling key), finds the real end of the block at
the next sibling mapping key, and detects the existing item indent so
the new entry matches it. Two regression tests cover the PyYAML-default
style; the existing 4-space-nested test still passes.

End-to-end verified against a real `hermes-agent` install on the exact
bug-triggering config: `hermes mcp list` shows codegraph as enabled,
`hermes tools --summary` lists both `mcp-codegraph` and `codegraph` in
the CLI toolset, and `hermes mcp test codegraph` connects in 264ms and
discovers all 10 codegraph tools. Re-running `codegraph install`
reports `Unchanged` and the file still has exactly one entry. Closes #456.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

__tests__/installer-targets.test.ts

@@ -635,6 +635,86 @@ describe('Installer targets — partial-state idempotency', () => {
     expect(body).toContain('custom:\n  keep: true');
   });
 
+  // Regression for #456: PyYAML's default block style writes list items at the
+  // SAME indent as the parent key (`cli:` and its `- hermes-cli` are both at
+  // indent 2). The pre-fix line-based patcher mistook that first list item for
+  // the next sibling key, truncated the cli block, and spliced `- mcp-codegraph`
+  // at indent 4 BEFORE the existing items — producing unparseable YAML.
+  it('hermes: install preserves PyYAML-default list-at-same-indent style (issue #456)', () => {
+    const hermes = getTarget('hermes')!;
+    const config = path.join(tmpHome, '.hermes', 'config.yaml');
+    fs.mkdirSync(path.dirname(config), { recursive: true });
+    const original = [
+      'model:',
+      '  default: gpt-4o',
+      'platform_toolsets:',
+      '  cli:',
+      '  - hermes-cli',
+      '  - browser',
+      '  - clarify',
+      '  - terminal',
+      '  - web',
+      '  telegram:',
+      '  - hermes-telegram',
+      '  discord:',
+      '  - hermes-discord',
+      '',
+    ].join('\n');
+    fs.writeFileSync(config, original);
+
+    hermes.install('global', { autoAllow: true });
+    const body = fs.readFileSync(config, 'utf-8');
+
+    // mcp-codegraph appended at the same 2-space indent as existing items
+    expect(body).toContain('\n  - mcp-codegraph\n');
+    // hermes-cli preserved
+    expect(body).toContain('\n  - hermes-cli\n');
+    // Sibling sections kept their indent — `telegram:` is still a key under
+    // platform_toolsets, not promoted up.
+    expect(body).toContain('\n  telegram:\n  - hermes-telegram\n');
+    expect(body).toContain('\n  discord:\n  - hermes-discord\n');
+    // No list items leaked to the platform_toolsets level (indent 0).
+    expect(body).not.toMatch(/^- browser/m);
+    expect(body).not.toMatch(/^- hermes-telegram/m);
+
+    // The whole platform_toolsets block extracted by line search should
+    // start with `cli:` and not contain a stray 4-space `mcp-codegraph`
+    // appearing before the rest of the existing items.
+    expect(body).toContain('  cli:\n  - hermes-cli\n  - browser');
+
+    // Idempotent
+    const second = hermes.install('global', { autoAllow: true });
+    expect(second.files[0]?.action).toBe('unchanged');
+  });
+
+  it('hermes: uninstall reverses the install on a PyYAML-default config', () => {
+    const hermes = getTarget('hermes')!;
+    const config = path.join(tmpHome, '.hermes', 'config.yaml');
+    fs.mkdirSync(path.dirname(config), { recursive: true });
+    const original = [
+      'platform_toolsets:',
+      '  cli:',
+      '  - hermes-cli',
+      '  - browser',
+      '  telegram:',
+      '  - hermes-telegram',
+      '',
+    ].join('\n');
+    fs.writeFileSync(config, original);
+
+    hermes.install('global', { autoAllow: true });
+    const installed = fs.readFileSync(config, 'utf-8');
+    expect(installed).toContain('- mcp-codegraph');
+    expect(installed).toContain('codegraph:');
+
+    hermes.uninstall('global');
+    const body = fs.readFileSync(config, 'utf-8');
+    expect(body).not.toContain('mcp-codegraph');
+    expect(body).not.toContain('command: codegraph');
+    expect(body).toContain('  cli:\n  - hermes-cli\n  - browser');
+    expect(body).toContain('  telegram:\n  - hermes-telegram');
+  });
+
   it('opencode: uninstall removes only mcp.codegraph, preserves comments and siblings', () => {
     const opencode = getTarget('opencode')!;
     const dir = path.join(tmpHome, '.config', 'opencode');