[eitsupi]

Raise the minimum VS Code version to 1.101.0 (Node.js 22) and remove the httpgd compatibility path for hosts without native WebSocket support.

Closes #1850

[renkun-ken]

Reviewed commit 44bd158. No actionable defects introduced by this PR.

Verified the new minimum in an actual VS Code 1.101.0 extension host: Electron 35.5.1 / Node 22.15.1 provides native WebSocket, and the authenticated handshake and plot-notification test passes there. The engine range, VS Code typings, lockfile, extension build target, README and upgrade note are consistent. Polling still handles failed connections, timeouts and disconnects; the standalone session agent retains its Node 18 target.

Validation:

• Frozen-lockfile install, production bundle, TypeScript compilation, lint and diff whitespace check passed.
• All 28 focused httpgd client, HTTP transport and SVG tests passed both locally on Node 26.12.0 and inside VS Code 1.101.0.
• All six current CI checks passed against this exact commit, including macOS, Ubuntu and Windows tests.

The production build emits two EJS render import warnings in unchanged code. They also reproduce with the previous esbuild configuration, and the corresponding imports and EJS dependency are unchanged from the base; these are outside this PR's scope.