scripts: add walkthrough:* convenience commands

Five new package.json scripts wrapping the most common walkthrough
flows, so contributors don't have to remember the flags:

  walkthrough:build        Regenerate the walkthrough in dev layout.
  walkthrough:build:prod   Regenerate with --minify + --base-path
                           matching the GH Pages deploy shape.
  walkthrough:serve        Start the local HTTP server on :8080.
  walkthrough:dev          Build + serve in one command.
  walkthrough:deploy:val   Upload val/*.ts to Val Town.

The bare `walkthrough` script still works for any other subcommand
(token, doctor, deploy-val with flags, etc.) — these are sugar, not
replacements.

Author: jdalton

package.json

@@ -61,7 +61,12 @@
     "type": "tsgo --noEmit -p .config/tsconfig.check.json",
     "update": "node scripts/update.mts",
     "update:data:npm": "node scripts/update-data-npm.mts",
-    "walkthrough": "node scripts/walkthrough.mts"
+    "walkthrough": "node scripts/walkthrough.mts",
+    "walkthrough:build": "node scripts/walkthrough.mts generate walkthrough.json",
+    "walkthrough:build:prod": "node scripts/walkthrough.mts --minify --base-path=/socket-packageurl-js generate walkthrough.json",
+    "walkthrough:serve": "node scripts/walkthrough.mts serve",
+    "walkthrough:dev": "node scripts/walkthrough.mts generate walkthrough.json && node scripts/walkthrough.mts serve",
+    "walkthrough:deploy:val": "node scripts/walkthrough.mts deploy-val"
   },
   "devDependencies": {
     "@anthropic-ai/claude-code": "2.1.92",