POC: F5 launch config, README, and implementation plan (Feature #2)

.vscode launch/tasks wire F5 -> Run Extension (preLaunchTask: npm build).
README documents run/dev. Plan archived under docs/superpowers/plans/.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.vscode/tasks.json

@@ -0,0 +1,13 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "type": "npm",
+      "script": "build",
+      "group": "build",
+      "problemMatcher": ["$esbuild"],
+      "label": "npm: build",
+      "detail": "Bundle the extension with esbuild"
+    }
+  ]
+}