Summary

gbrain frontmatter validate <path> (and by extension the frontmatter_integrity check in gbrain doctor) walks every subdirectory under <path>, including node_modules/, .git/, and other non-content directories. This produces large false-positive counts of MISSING_OPEN warnings on any source repo that vendors npm packages.

The sibling gbrain frontmatter generate walker filters these directories correctly. The two walkers should behave consistently.

Repro

```bash
mkdir test-source && cd test-source
npm init -y && npm i express
gbrain sources add test --path "$(pwd)"
gbrain doctor 2>&1 | grep frontmatter_integrity
```

Expected: 0 issues (no content yet).
Actual: tens to hundreds of `MISSING_OPEN` issues, all inside `node_modules/`.

I hit this on a real-world setup pointing gbrain at a TypeScript project (Bun + node_modules + a docs/ folder). 7 real content issues got drowned in 226 false positives from npm package READMEs.

Root cause

Two walkers in `src/commands/frontmatter.ts`:

• `generate` walker (line ~421) correctly skips:
  ```ts
  if (entry === '.git' || entry === 'node_modules' || entry === '.obsidian') continue;
  ```

• `validate` walker (lines ~243–264) has no such filter. It pushes every directory onto its DFS stack and only filters per-file via `isSyncable`, which doesn't reject the `node_modules` prefix.

Result: doctor's `frontmatter_integrity` check (which uses the validate path) reports inflated counts that operators cannot resolve via `--fix` since the files aren't theirs. The warning becomes load-bearing noise that erodes trust in doctor's output.

Suggested fix

Add the same skip predicate to the validate walker:

```ts
for (const name of entries) {
if (name === '.git' || name === 'node_modules' || name === '.obsidian') continue;
// ...existing per-entry logic
}
```

Both walkers should ideally share a single helper (`shouldSkipDirEntry(name)`) to prevent this from drifting again.

Environment

• gbrain v0.33.0
• Windows 11, Bun 1.3.13
• Postgres engine (Supabase pooler)
• Reproduces against vanilla `node_modules/` from `npm init`

Notes

Happy to send a PR for the one-line fix if useful — let me know.