Sanitization 2.1.0

sanitization 2.1.0

This release adds an isolated compatibility path for projects migrating from
secrecy 0.10 while preserving the stricter exposure and storage contracts of
the native sanitization containers.

Secrecy compatibility companion

• Add the sanitization-secrecy sister crate with SecretBox<S>,
  SecretSlice<S>, SecretString, ExposeSecret, and ExposeSecretMut.
• Add explicit CloneableSecret support and optional plaintext Serde through
  SerializableSecret.
• Bound SecretString Serde loading to 1 MiB by default and isolate generic,
  inherently unbounded SecretBox<T> loading behind the explicit
  serde-compat-unbounded feature.
• Provide the familiar new, init_with_mut, init_with, and
  try_init_with constructors. Temporary values used by cloning constructors
  are protected by a sanitizing unwind guard, and clone-based constructors
  require the explicit CloneableSecret partial-destination cleanup contract.
• Add try_init_with_mut, runtime-length final-allocation byte-slice
  initialization, exact-capacity no-copy vector transfer, and data-oblivious
  equality with explicit call-site declassification.
• Require audited shared and mutable storage-stability contracts for
  SecretBox reference exposure and mutable initialization under every feature
  combination. The explicit hazmat-unrestricted-exposure feature adds a
  visibly distinct UnrestrictedSecretBox rather than weakening existing
  trait implementations through Cargo feature unification.
• Make runtime-length byte-slice allocation genuinely fallible and add
  try_init_with_len_bounded::<MAX, _> so untrusted lengths are rejected
  before allocation or initialization with typed build/initializer errors.
• Clear complete owned String and Vec source capacities during boxed
  conversion, and sanitize completed destination elements if a later slice
  clone unwinds.
• Build cloned slices directly in exact boxed storage with initialized-prefix
  unwind cleanup and a mandatory full-initialization assertion before the guard
  is disarmed, avoiding allocator-dependent Vec capacity assertions, and
  restrict automatic array clone authorization to reviewed integer arrays.
• Make explicit consumption sanitize exactly once and add diagnostic-matching
  regression coverage for the clone authorization marker.
• Correct full-capacity String wiping to use allocation-wide vector
  provenance, preserving UTF-8 validity during optional multi-pass clearing
  and covering excess-capacity strings under Miri.
• Re-export zeroize by default and implement Zeroize/ZeroizeOnDrop for
  the compatibility wrapper by delegating to SecureSanitize.
• Support Cargo package aliasing so many existing secrecy::... imports can
  remain unchanged during incremental migration.
• Add downstream package-alias tests, no-default/all-feature tests, Miri
  coverage, package verification, and release-script integration.

Core support

• Add SecureSanitize for str, routing its single unsafe byte-view
  conversion through the existing audited wipe backend. Replacing every byte
  with ASCII NUL preserves UTF-8 validity and enables fixed boxed strings to be
  cleared without allocation.

Security scope

The compatibility wrappers intentionally do not add reference-returning
exposure, cloning, or plaintext serialization to native hardened containers.
They provide baseline boxed ownership and clear-on-drop behavior, not memory
locking, guard pages, canaries, storage-history recovery, or closure-confined
exposure. SecretString remains unconditionally cloneable for upstream source
compatibility; other custom cloneable values must implement both
SecureSanitize and CloneableSecret.

All six workspace crates are coordinated at version 2.1.0. The runtime keeps
an exact dependency on the matching derive crate, and companions retain caret
requirements on the core runtime.