[sdk-client S2] feat(sdk): define NetScriptProcedureMeta without erasing contract errors

[rickylabs]

Part of #1348. Implements RFC 0001 stage 1b.

Summary

Initialize and export the NetScript-owned procedure metadata vocabulary required by typed client contributions while preserving the concrete error channel repaired by #1350. Metadata must remain independent of oRPC public types and must propagate through generated client declarations.

Acceptance

• NetScriptProcedureMeta has a public, versionable NetScript-owned shape.
• Existing contract error literals remain preserved end to end.
• Metadata reaches direct clients, generated clients, and query factories without casts or any.
• Positive and negative type fixtures exercise real exports.
• Public docs explain ownership and compatibility boundaries.
• Required SDK/contracts gates and IMPL-EVAL pass.