Context

Follow-up hardening items identified during review of #2077 (feat(policy): support custom preset files via --from-file / --from-dir), which implements the custom preset surface requested in #2039.

These were intentionally deferred from #2077 to keep scope focused on the core feature. None are blockers — all are defense-in-depth or developer-experience improvements.

Items

From PR review (suggestions)

• File size guard in loadPresetFromFile — add a statSync(abs).size check with a reasonable limit (e.g. 1 MB) before readFileSync to avoid reading unexpectedly large files.
• Temp file cleanup in tests — the writeTmp helper in test/policies.test.ts creates temp directories but never cleans them up. Add afterEach cleanup or vi.onTestFinished.
• Dotfile filtering for --from-dir — readdirSync + .ya?ml filter picks up files like .hidden-preset.yaml. Add .filter(f => !f.startsWith('.')) to match typical directory-scan behavior.
• Symlink check in loadPresetFromFile — loadPresetFromFile uses fs.statSync which follows symlinks. Low blast radius since the user already has filesystem access, but worth noting for defense-in-depth (built-in loadPreset has path traversal protection).

From CodeRabbit review (deferred)

• --dry-run merged-policy diff renderer — currently --dry-run prints endpoints that would be opened/removed. A real policy-diff renderer (structured YAML diff, colorization, tombstone handling on remove) should improve --dry-run for all policy-add and policy-remove paths, not just --from-file/--from-dir.
• Non-hermetic NEMOCLAW_OPENSHELL_BIN env handling in tests — the delete process.env.NEMOCLAW_OPENSHELL_BIN idiom predates feat(policy): support custom preset files via --from-file / --from-dir (closes #2039) #2077 and affects multiple test call sites. Introduce a shared withEnv helper in a single chore(test) sweep.

References

• Original issue: [CLI] nemoclaw policy-add has no custom-preset surface; custom egress targets require dropping to openshell policy set #2039
• Implementation PR: feat(policy): support custom preset files via --from-file / --from-dir (closes #2039) #2077