Migrate LSP client to vscode-jsonrpc for improved stability (#1095)

* refactor(lsp): migrate to vscode-jsonrpc for improved stability

Replace custom JSON-RPC implementation with vscode-jsonrpc library.
Use MessageConnection with StreamMessageReader/Writer.
Implement Bun↔Node stream bridges for compatibility.
Preserve all existing functionality (warmup, cleanup, capabilities).
Net reduction of ~60 lines while improving protocol handling.

* fix(lsp): clear timeout on successful response to prevent unhandled rejections

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Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

package.json

@@ -64,6 +64,7 @@
     "jsonc-parser": "^3.3.1",
     "picocolors": "^1.1.1",
     "picomatch": "^4.0.2",
+    "vscode-jsonrpc": "^8.2.0",
     "zod": "^4.1.8"
   },
   "devDependencies": {