(3/6) validate mount policy paths

[philipnee]

Why

Client permissions are a load-bearing security boundary. The schema accepted empty action grants, unsupported wildcard forms, and paths that did not point at any configured mount or proxy source. That made typoed policies easy to miss until runtime.

What changed

• Require each permission entry to include at least one action.
• Reject permission wildcards except the supported trailing /** subtree form.
• Validate permission paths against configured mount paths and legacy proxy source roots.
• Reject wildcard mount paths.
• Normalize mount paths before duplicate-path detection.
• Expand config tests for invalid policy paths, empty action lists, global grants, nested mount grants, and wildcard mount paths.

How

The config superRefine pass now builds known policy roots from mounts and proxy source ids, then checks every client permission against those roots. The global /** permission remains valid for all-source clients.

Changed files

• src/config/schema.ts
• tests/config.test.ts

Verification

• npm test -- tests/config.test.ts
• npm run verify