[Feat] VS Code extension

[ax1s-x1zz]

Context

docs/ROADMAP.md Track E-1. Editor integration built on the LSP server.

Scope

• LSP client + runner integration
• In-editor run/check with policy-gate output

Acceptance

Run xazz check-equivalent diagnostics from the editor without touching a terminal.

Dependencies

Depends on B-3 (LSP).

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See docs/ROADMAP.md for the full scale plan and execution order.