The REAL_JWE_TOKEN constant in otp-flow.test.ts contained an actual
token captured from a live Perplexity auth response. Replace with a
structurally valid but non-functional placeholder.
Enforce 0600 permissions after every auth token write so existing files
with broader modes are corrected.
Add a regression test for the permission hardening path and document the
Bun runtime dependency used by the Node/jiti search subprocess path.
Also declare bun in package dependencies and engines.