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/launch.json

@@ -0,0 +1,13 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Run Extension",
+      "type": "extensionHost",
+      "request": "launch",
+      "args": ["--extensionDevelopmentPath=${workspaceFolder}"],
+      "outFiles": ["${workspaceFolder}/out/**/*.cjs"],
+      "preLaunchTask": "npm: build"
+    }
+  ]
+}