fix(mcp): handle cold wake in handleMcpMessage RPC entry point

[threepointone]

Summary

Fixes #1282.

• McpAgent.handleMcpMessage is a native DO RPC method that bypasses PartyServer's fetch/alarm/webSocket entry points where #ensureInitialized() normally runs. When the MCP server DO wakes from hibernation via this path, this.name was never hydrated from storage, causing a crash.
• Replaced the hand-rolled 15-line cold-start block inside handleMcpMessage with a single await this.__unsafe_ensureInitialized() call, matching the pattern used by _workflow_handleCallback, _workflow_broadcast, _workflow_updateState, and alarm().
• This eliminates a duplicate initialization path that was both incomplete (missed name hydration) and divergent from onStart (missed Agent-level MCP client restore, workflow checks, etc.).

Test plan

• Added two regression tests that simulate cold wake by seeding __ps_name directly in storage (bypassing setName/onStart), then calling handleMcpMessage as the first entry point
• First test verifies initialize message succeeds after cold wake
• Second test verifies full tool call flow works after cold wake
• All 26 RPC transport tests pass
• Build passes
• Type checks pass

Made with Cursor

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Latest commit: 3b632d7

The changes in this PR will be included in the next version bump.

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commit: 3b632d7