feat(core): OSCAL assessment-results emitter + finding->control linker

Assess our findings against catalog controls and emit a standard OSCAL 1.1
assessment-results document — the assessment half of the loop (their catalog,
our assessment).

- ControlLinker maps a Finding's CWE -> catalog control-ids (CRA seed mirrors
  breakpilot's _CWE_TO_REQ; extensible via ControlLinker::new)
- assess() builds an observation per linked finding + a per-control
  'not-satisfied' finding; reviewed-controls covers the full catalog set
- deterministic: stable uuid5 ids (adds uuid "v5" feature) + caller-supplied
  timestamp; pure (no DB/network)
- 3 lib tests

Not yet wired into a scan run — that lands with the control-driven router (PR-4).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.toml

@@ -28,7 +28,7 @@ reqwest = { version = "0.12", features = ["json", "rustls-tls", "multipart", "co
 thiserror = "2"
 sha2 = "0.10"
 hex = "0.4"
-uuid = { version = "1", features = ["v4", "serde"] }
+uuid = { version = "1", features = ["v4", "v5", "serde"] }
 secrecy = { version = "0.10", features = ["serde"] }
 regex = "1"
 zip = { version = "2", features = ["aes-crypto", "deflate"] }