[do not merge] patch so XWing Obsolete has a valid code path

[insipx]

KEM math is identical between the two variants — only the codepoint mixed into HPKE suite_id labels (and thus AEAD keys) differs. Lets clients pin to the obsolete 0x004D codepoint for wire compat with peers on hpke-rs 0.4.x.

Based on v0.6.1.

can be deleted after d14n migration

Note

Add valid code path for KemAlgorithm::XWingDraft06Obsolete in libcrux provider

Routes KemAlgorithm::XWingDraft06Obsolete through the same logic as XWingDraft06 in kem_key_gen, supports_kem, and kem_key_type_to_libcrux_alg in lib.rs. Previously, this variant had no valid code path and would error. #[allow(deprecated)] is added to the relevant match arms to suppress deprecation warnings.

^{Macroscope summarized 3425025.}

[macroscopeapp]

Approvability

Verdict: Approved

Mechanical fix adding the existing XWingDraft06Obsolete enum variant to match arms in libcrux_provider, mirroring the same pattern already used throughout the codebase. No new behavior introduced - just completing exhaustive pattern matching with identical handling.

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