Show constructor signatures on state machine arrows - #120

Summary

Show the constructor signature on each initial state machine arrow. Keep conditional postconditions available under the existing Expand Conditions toggle, and accept responses from older servers that lack signature metadata.

Implements the diagram side of #112. Parser metadata comes from liquid-java/liquidjava-fsm#1.

Verification

• Client webpack compile and server Maven build passed.
• Headless VS Code diagnostic smoke test passed.
• In a live VS Code webview built with the FSM parser branch, the state machine rendered new MultipleInitialStates() and new MultipleInitialStates(int) on separate initial arrows.

Local review

1. Check out Record constructor signatures on initial state transitions liquidjava-fsm#1 and run mvn install there.
2. Check out this PR, then run npm ci and npm run build:server in client.
3. Open client in VS Code and press F5. In the Extension Development Host, open a Java class with overloaded state-refined constructors and view its State Machine tab.

The server still pins the published FSM 0.1.0 dependency. Maven must use the locally installed parser build for this test; a new FSM artifact version and server dependency update are needed before release.