fix(lobby): share protocol version with worker

[matthewevans]

No description provided.

[gemini-code-assist]

Code Review

This pull request consolidates the wire-protocol version constants into the lobby-broker Rust crate, exporting them to server-core and exposing them to the Cloudflare Worker shell via WASM. This eliminates the hand-written TypeScript protocol stub and introduces a build-time check script to prevent client-server protocol drift. Feedback is provided regarding unsafe NaN handling in the protocol version check which could bypass handshake validation, and fragile regex patterns in the version check script that are sensitive to minor formatting changes.

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[gemini-code-assist]

[HIGH] Unsafe NaN handling in protocol version check. Evidence: lobby-worker/src/hello-gate.ts:25-28.
Why it matters: If the client sends a non-numeric or malformed protocol_version, Number(...) returns NaN, which makes all comparison checks evaluate to false and incorrectly accepts the handshake.
Suggested fix: Explicitly check for NaN or default to 0 when parsing fails to ensure malformed versions are rejected.

      const protocolVersion = Number(frame.data?.protocol_version);
      if (
        Number.isNaN(protocolVersion) ||
        protocolVersion < minSupportedProtocol ||
        protocolVersion > serverProtocolVersion
      )

[gemini-code-assist]

[MED] Fragile regex patterns for version extraction. Evidence: scripts/check-protocol-version.mjs:26.
Why it matters: The current regex patterns are sensitive to minor formatting changes (such as spacing around colons or equals signs) and could cause unexpected build failures.
Suggested fix: Use more robust regex patterns that allow flexible whitespace.

Suggested change

	const rustVersion = extractVersion(
	rustSource,
	/pub const PROTOCOL_VERSION: u32 = (\d+);/,
	"crates/lobby-broker/src/protocol.rs",
	);
	const clientVersion = extractVersion(
	clientSource,
	/export const PROTOCOL_VERSION = (\d+);/,
	"client/src/adapter/ws-adapter.ts",
	);
	const rustVersion = extractVersion(
	rustSource,
	/pub\s+const\s+PROTOCOL_VERSION\s*:\s*u32\s*=\s*(\d+)\s*;/,
	"crates/lobby-broker/src/protocol.rs",
	);
	const clientVersion = extractVersion(
	clientSource,
	/export\s+const\s+PROTOCOL_VERSION\s*=\s*(\d+)\s*;/,
	"client/src/adapter/ws-adapter.ts",
	);