docs(crypto): clarify encryptable contract

[quexten]

Encryptables currently have mis-usages, which lead to easy bugs. For example, encrypt(decrypt(encrypt(K1), K1), K2) may lead to an item partially being encrypted by K1, and partially by K2. The next decrypt will fail. This is entirely unexpceted and a footgun. This PR adds clarification on the intent (contract) of the traits, and tags usages that are violating the contract.

[github-actions]

🔍 SDK Breaking Change Detection

SDK Version: cipher-full-view-part-1 (7238134)

⚠️ If breaking changes are detected, a corresponding pull request addressing them must be ready for merge in the affected client repository.

Client	Status	Details
typescript	✅ No breaking changes detected	Compilation passed with new SDK version - View Details
android	✅ No breaking changes detected	Compilation passed with new SDK version - View Details

---

Breaking change detection uses the build of the SDK from this branch, including any incompatibities pre-existing on or merged into this branch. Check the workflow logs to confirm.
Results update as workflows complete.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.74%. Comparing base (e504886) to head (7238134).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1286   +/-   ##
=======================================
  Coverage   85.74%   85.74%           
=======================================
  Files         483      483           
  Lines       68364    68364           
=======================================
  Hits        58622    58622           
  Misses       9742     9742           

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[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

This is a documentation-only change to bitwarden-crypto and bitwarden-vault. It adds a round-trip contract to the CompositeEncryptable, PrimitiveEncryptable, and Decryptable traits, then annotates the existing AttachmentView, CipherView, and LoginView implementations that violate that contract by passing key-bound ciphertext (key, fido2_credentials) through unchanged. I verified each annotation against the surrounding code — the described pass-through behavior, field types, and the reencrypt_fido2_credentials escape hatch all match reality. No executable code changes are present, so there is no runtime behavior or security impact.

Code Review Details

No blocking findings.

Minor note (not blocking): crates/bitwarden-crypto/src/traits/decryptable.rs:8 contains a typo — "MUST succed" should be "MUST succeed".

[eligrubb]

Love it!