dev: add .vscode launch/tasks so F5 launches the extension host

Without launch.json, F5 in a fresh clone just prompts for a debug
environment. The 'Run Extension' configuration spawns an Extension
Development Host with this workspace loaded, with `npm: compile` as
a preLaunchTask so the extension always runs against an up-to-date
build.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.vscode/tasks.json

@@ -0,0 +1,27 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "type": "npm",
+      "script": "compile",
+      "group": "build",
+      "problemMatcher": "$tsc",
+      "label": "npm: compile",
+      "presentation": {
+        "reveal": "silent",
+        "clear": true
+      }
+    },
+    {
+      "type": "npm",
+      "script": "watch",
+      "group": "build",
+      "problemMatcher": "$tsc-watch",
+      "isBackground": true,
+      "label": "npm: watch",
+      "presentation": {
+        "reveal": "silent"
+      }
+    }
+  ]
+}