[LevK]: Build and test as a standalone package

Split out of actions/toolkit (packages/http-client, history kept by filter-repo).
Brings the 2024 [LevK] packaging edits forward onto current upstream:

- tsconfig.json: the monorepo root's compiler options inlined, no extends
- jest.config.cjs: the root's ts-jest transform, rooted at tests/
  (isolatedModules: ESM lib/ and sources run through CommonJS)
- __tests__/ -> tests/
- package.json: test = jest, build = tsc; jest/ts-jest/typescript as
  devDependencies; repository, homepage, bugs on git.levk.dev
- .gitignore: node_modules/, lib/, audit.json
- HttpCodes.PayloadTooLarge = 413 (the 2024 edit; still missing upstream)

Not carried over from 2024: the _getExistingOrDefaultHeader type
narrowing (upstream has since fixed it properly), version reset to 1.0.0 (dependents' ranges
need upstream's numbering) and the Unlicense field (the code is MIT).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UHXzGrsxfkGk8LmwrBbHNZ

package.json

@@ -7,7 +7,7 @@
     "actions",
     "http"
   ],
-  "homepage": "https://github.com/actions/toolkit/tree/main/packages/http-client",
+  "homepage": "https://git.levk.dev/actions/http-client",
   "license": "MIT",
   "type": "module",
   "main": "lib/index.js",
@@ -21,18 +21,18 @@
       "types": "./lib/auth.d.ts",
       "import": "./lib/auth.js"
     },
-    "./lib/proxy": {  
-      "types": "./lib/proxy.d.ts",  
+    "./lib/proxy": {
+      "types": "./lib/proxy.d.ts",
       "import": "./lib/proxy.js"
     },
-    "./lib/interfaces": {  
-      "types": "./lib/interfaces.d.ts",  
+    "./lib/interfaces": {
+      "types": "./lib/interfaces.d.ts",
       "import": "./lib/interfaces.js"
     }
   },
   "directories": {
     "lib": "lib",
-    "test": "__tests__"
+    "test": "tests"
   },
   "files": [
     "lib",
@@ -43,25 +43,28 @@
   },
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/actions/toolkit.git",
-    "directory": "packages/http-client"
+    "url": "https://git.levk.dev/actions/http-client.git"
   },
   "scripts": {
     "audit-moderate": "npm install && npm audit --json --audit-level=moderate > audit.json",
-    "test": "echo \"Error: run tests from root\" && exit 1",
+    "test": "jest",
     "build": "tsc",
     "format": "prettier --write **/*.ts",
     "format-check": "prettier --check **/*.ts",
     "tsc": "tsc"
   },
   "bugs": {
-    "url": "https://github.com/actions/toolkit/issues"
+    "url": "https://git.levk.dev/actions/http-client/issues"
   },
   "devDependencies": {
+    "@types/jest": "^29.5.4",
     "@types/node": "24.1.0",
+    "@types/proxy": "^1.0.1",
     "@types/tunnel": "0.0.3",
+    "jest": "^29.6.4",
     "proxy": "^2.1.1",
-    "@types/proxy": "^1.0.1"
+    "ts-jest": "^29.1.1",
+    "typescript": "^5.2.2"
   },
   "dependencies": {
     "tunnel": "^0.0.6",