error-compliance.yaml: add release-precision VERSION_UNSUPPORTED probe (#3570 follow-up)

[bokelley]

Context

static/compliance/source/universal/error-compliance.yaml (phase version_negotiation, step at ~line 341-383) probes VERSION_UNSUPPORTED by sending adcp_major_version: 99 (integer field). With 3.1 promoting release-precision negotiation to the primary wire field, the error-path coverage should also exercise an unknown release-precision pin (e.g., adcp_version: "99.0").

Without this addition, a seller could implement integer-only VERSION_UNSUPPORTED validation and pass all storyboards while shipping a broken 3.1 buyer experience — the new version_negotiation universal storyboard (#4702) covers advertise + echo but explicitly defers the error path.

What to add

A parallel step in the same phase that:

• Sends adcp_version: "99.0" (release-precision shape, unsupported value)
• Asserts error_code: VERSION_UNSUPPORTED
• Asserts error.data.supported_versions[] is present and non-empty (per static/schemas/source/error-details/version-unsupported.json)

Advisory at 3.1, promoted with the rest of the version-negotiation suite at the 3.2 storyboard cut.

Refs

• Tier 1 epic: Epic: Tier 1 — version-negotiation work before 3.1 GA #3570
• Universal storyboard PR: docs+compliance: 3.1 release notes + version-negotiation storyboard (#3570) #4702
• Error-details schema: static/schemas/source/error-details/version-unsupported.json

[bokelley]

Shipped — static/compliance/source/universal/error-compliance.yaml already contains the unsupported_release_version step at line 385:

• Sends adcp_version: "99.0" (release-precision shape)
• Asserts error_code: VERSION_UNSUPPORTED
• Documents the error.data.supported_versions[] expectation
• Marked severity: advisory for 3.1, promotes with the rest of the version-negotiation suite at the 3.2 storyboard cut

Likely shipped via #4779 (3.1.0 docs + scenario sweep) which references this issue. Closing.