Extend C-328 to the full-response http family on the embedded lane

[O6lvl4]

Refs almide/almide#3620

C-328 said the full-response http family (get_response … request_response) is native-only. The implementation now serves it on the embedded wasm lane (almide run --target wasm). The embedded host answers a framed op 65 from the same rt-core request_response the native leg calls, and the http_framed splice rebuilds the HttpResponse value from that answer. This PR records that in the ledger before the implementation lands, as the boundary rule requires.

Changes

• C-328 statement: an EXTENDED clause (appended; the earlier text is kept as history). It says:
  • the family is served on the embedded lane;
  • what op 65 answers;
  • that status, every header line (wire order, repeats kept) and the body read the same through the accessors on native and embedded;
  • that the NATIVE-ONLY sentence now holds for the stock-p1 and p3 lanes only.
• New fixture: spec/embedded_cross/http_response_errs.almd (// @contract: C-328) runs the six verbs against closed ports, a malformed url, an unsupported scheme and a refused header value. It is listed as C-328 evidence.
• docs/contracts/conformance.md regenerated.

Evidence

• Before pinning, the fixture was run on native and on the embedded lane with the implementation branch's binary: byte-identical stdout, exit 0 on both.
• The judge runner has no embedded leg; the implementation's tests/embedded_cross_test.rs runs every spec/embedded_cross fixture native against embedded.
• The success path (a 200 with a repeated Set-Cookie, a 404, an unfollowed 302, an echoed header) is covered by the implementation-side tests/http_response_cross_test.rs. That test will be cited in the implementation's ledger once it lands there, not here.
• Every gate in CLAUDE.md's pre-commit list passes locally: contracts, provenance, element coverage, style, validation, links, gate verification, the conformance self-test, runner coverage.

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