fix(rvf): reject unknown capability names

[proffesor-for-testing]

Summary

• detect non-empty unknown names in plaintext capability declarations
• fail capability verification and retain a deny-all mapping
• emit a distinct CapabilityUnknown witness detail and UnknownCapability error
• preserve empty, whitespace-normalized, encrypted, and absent declaration behavior

Fixes #23

Verification

• cargo test -p rvm-rvf (100 passed)
• cargo clippy -p rvm-rvf --all-targets -- -D warnings
• cargo check --workspace

TDD evidence

The mixed known/unknown declaration regression failed before implementation.

Adversarial review

NO BLOCK after one REMAND. The first green implementation produced the wrong public error (UnsupportedCapability(Randomness)) for unknown names. Added a second red regression and a stable UnknownCapability path. Checked later META segments, mixed known/unknown names, whitespace, empty entries, and deny-all behavior.