#428 Bump hey-sdk to v0.30.0

Summary

Pins hey-sdk v0.30.0 (go/v0.30.0, 9b16fc7).

What it brings the CLI:

• Draft sends and edits that HEY rejects with a 422 now surface the validation message instead of a bare "validation error", and a draft edit that fails no longer reads as applied (basecamp/hey-sdk#133). Closes #350.
• Also in the release, not yet called here: the workflow stage reader (basecamp/hey-sdk#141), generated operation retry policies (basecamp/hey-sdk#94), Retry-After rounding (basecamp/hey-sdk#151), and the Rust SDK (basecamp/hey-sdk#145).

Alongside the pin:

• internal/mcpserver/model/ resynced from go/v0.30.0 via make update-mcp-model: PROVENANCE moves to 9b16fc7, and the model gains GetWorkflowStage under the Workflows tag, which the catalog already pins as unmapped, so TestCatalogUnmappedTagsArePinned is unchanged.
• github.com/oapi-codegen/runtime v1.6.0 → v1.7.0 (indirect, pulled by the SDK).
• nix/package.nix vendorHash recomputed with make update-nix-hash and verified by a full Nix build.

Test plan

• make check (fmt, vet, lint, unit tests, tidy, surface, release lockstep)
• make update-nix-hash built the flake against the new go.sum
• go.mod carries a single github.com/basecamp/hey-sdk/go v0.30.0 requirement and no replace

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Summary by cubic

Pins hey-sdk from v0.29.0 to v0.30.0, so draft sends and edits HEY rejects with a 422 now surface the validation message instead of a bare "validation error", and a failed draft edit no longer reads as applied.

Changes

• The MCP model resyncs to go/v0.30.0, adding GetWorkflowStage under the Workflows tag, which the catalog already pins as unmapped.
• github.com/oapi-codegen/runtime bumps to v1.7.0 as an indirect dependency.
• nix/package.nix vendorHash is recomputed via make update-nix-hash and verified with a full Nix build.
• Other SDK additions like the workflow stage reader and retry policy fixes are not called by the CLI yet.