feat(settings): add the passkey wrap creation hook

[vpomerleau]

Because

• Passwordless Sync must seal kB to a passkey's PRF output before a wrap can be stored.
• The store is create-only, so a bad or duplicated envelope wedges the credential until
  the passkey is re-enrolled.

This pull request

• Adds lib/passkeys/wrap/: createPasskeyWrapFlow seals kB into a wrap envelope and
  stores it under an mfa:passkey proof; usePasskeyWrapCreation wraps it in React state.
• Reads the account and credential from the proof's sub/cid before touching key
  material, so the sealing context always matches what the server files the wrap under.
• Reopens each envelope before storing it, and rejects missing, wrong-width or spent key
  material.
• Holds a sealed-but-unstored envelope in a store shared across instances, so a retry —
  including after a remount — re-sends identical bytes.
• Maps server errnos to distinct failure reasons and evicts a rejected proof from
  JwtTokenCache.
• Zeroes kB and the PRF output once sealed.

Issue that this pull request solves

Closes: FXA-14425

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

How to review (Optional)

• Key files/areas to focus on: wrap/interfaces.ts (the failure-reason union and
  result types) and wrap/creation.ts (the flow). The hook is a 60-line state wrapper.
  Tests and fixtures are ~65% of the diff.
• Suggested review order: interfaces.ts → creation.ts top to bottom →
  use-passkey-wrap-creation.ts → creation.test.ts, the retries and proof claims
  blocks.
• Risky or complex parts: the create-only store means a mis-sealed or re-sealed
  envelope wedges the credential permanently, so three guards do the heavy lifting: the
  reopen-before-store check, the held envelope shared across instances via
  passkeyWrapStore, and the cid/sub read from the proof before any key material is
  touched. kB/prfOut zeroing on every path is the other thing worth tracing.

Screenshots (Optional)

Please attach the screenshots of the changes made in case of change in user interface.

Other information (Optional)

Not exported from lib/hooks/index.ts or lib/passkeys/index.ts: the flow pulls in the
HPKE suite, which builds a CipherSuite at module scope. Consumers deep-import
lib/passkeys/wrap, as pages/Signin does with usePasskeySignIn.

[Copilot]

🟡 Changes recommended

Same-tick calls can corrupt hook state because early flow results never set flow.inFlight.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 7/7 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

🟡 Changes recommended

A mismatched-key retry discards the only byte-identical envelope and can wedge a credential after an ambiguous successful POST.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 7/7 changed files
• Comments generated: 1
• Review effort level: Balanced

[vpomerleau]

Working on a shorter version of this PR - will open as a new PR.