The OKF analogue of tests/test_showcase.py: one received external bundle plants
one attack per OKF surface (T1 body + frontmatter-description, T3 non-https
resource, T4 path-traversal + reserved-name, T2 dangerous frontmatter value,
T5a dangerous-scheme link, §7.2 dangling link, homoglyph-obfuscated body) run
through the public okf surface as an upload-inbox consumer would compose it.
Aggregate fails secure -> REJECT; a clean bundle admits (WARN); the log marks
rejected concepts. Detach-proof: an always-admit gate catches none of the
surfaces, so the assertions have teeth. Stream-2 centrepiece (PLAN §212);
Stage-1 realistic upload extraction (§247) is the next increment.
Tests 277 -> 282.
