Fix TelemetryReporter import to use named export in session.ts

`@vscode/extension-telemetry` exports `TelemetryReporter` as a named
class with no default export. We were importing it as a default, which
resolves to the module namespace object rather than the class, so using
it as the `telemetryReporter` parameter type tripped `tsc --noEmit` with
`error TS2709: Cannot use namespace 'TelemetryReporter' as a type`.

`npm run compile` uses esbuild, which doesn't type-check, so this slipped
through CI. This aligns `session.ts` with the named import already used
in `extension.ts`. The symbol is only used as a type here, so there's no
runtime change.

Drafted by Copilot (Claude Opus 4.8).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andyleejordan

src/session.ts

@@ -4,9 +4,10 @@
 import net = require("net");
 import path = require("path");
 import vscode = require("vscode");
-import TelemetryReporter, {
+import {
     type TelemetryEventMeasurements,
     type TelemetryEventProperties,
+    TelemetryReporter,
 } from "@vscode/extension-telemetry";
 import { Message } from "vscode-jsonrpc";
 import {