chore: standalone Halfstreet repo scaffolding

- package.json: drop @astrojs/sitemap, fontsource fonts, wrangler,
  @cloudflare/workers-types, tsx, spotify scripts. Keep astro/yaml/zod
  + vitest/typescript/@astrojs/check/@types/node. Add GPL-3.0-or-later.
- astro.config.mjs: drop sitemap integration, sharp image config; set
  site to halfstreet.io.
- tsconfig.json: drop cloudflare-workers-types, drop functions/scripts
  from include.
- .gitignore: cloudflare-free; Obsidian workspace cache rules updated
  to post-rename src/world/.obsidian/ paths.
- README.md: stack, layout, design-doc index, license note.
- .woodpecker.yml: install + npm test + npm run build pipeline.

package.json

@@ -0,0 +1,28 @@
+{
+  "name": "halfstreet",
+  "type": "module",
+  "version": "0.0.1",
+  "license": "GPL-3.0-or-later",
+  "engines": {
+    "node": ">=22.12.0"
+  },
+  "scripts": {
+    "dev": "astro dev",
+    "build": "astro check && astro build",
+    "preview": "astro preview",
+    "astro": "astro",
+    "test": "vitest run",
+    "test:watch": "vitest"
+  },
+  "dependencies": {
+    "astro": "^6.1.9",
+    "yaml": "^2.8.4",
+    "zod": "^4.4.3"
+  },
+  "devDependencies": {
+    "@astrojs/check": "^0.9.8",
+    "@types/node": "^25.6.0",
+    "typescript": "^5.9.3",
+    "vitest": "^4.1.5"
+  }
+}