One authority answers 'which credential may ride this request':
credential_class / manager_for / credential_for / bearer_resolver_for,
keyed by (platform, base_url). SessionCredential is an opaque type with
no production constructor, so a new call site cannot re-introduce the
session-bearer leak. Platform-scoped tests extended across all bearer
channels (session, aux, summary, subagent override).
Verified: cargo check --workspace --all-targets clean; kigi-shell and
kigi-tui suites green (6611+ tests).
ZacharyZhang-NY
48d89c7830