Address final pentest hardening pass

Author: eldryoth

docs/API_AUDIT.md

@@ -169,6 +169,9 @@ Decision rationale:
   initialized bytes and vector spare capacity.
 - `SecretBuffer` does not lock allocations into physical memory. OS paging,
   hibernation, and crash-dump controls remain deployment responsibilities.
+- `SecretBuffer` intentionally does not implement `Clone`; callers that need a
+  second copy must spell that out through `from_slice`, making secret
+  duplication visible at the call site.
 - Equality is intentionally not exposed through `PartialEq`/`==`. Callers must
   opt into the explicit `constant_time_eq_public_len` helper, whose equal-length
   scan is best-effort and whose length mismatch remains public.

docs/PANIC_POLICY.md

@@ -28,6 +28,10 @@ The current reviewed exceptions are:
   metadata. Calling it at runtime with a mismatched const output length can
   also unwind; do not route attacker-controlled sizing decisions through this
   API.
+- `LineWrap::new` may panic when `line_len == 0`. It is intended for fixed,
+  trusted values and profile constants. Use `LineWrap::checked_new` when a line
+  length comes from runtime configuration, file metadata, network input, or
+  another untrusted source.
 - Internal remainder matches use `_ => unreachable!()` after matching
   `len % 3` or equivalent remainder values. The preceding arithmetic bounds
   make those arms unreachable.