[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

tests/keepalive.test.ts

@@ -0,0 +1,79 @@
+import * as httpm from '../lib'
+
+describe('basics', () => {
+  let _http: httpm.HttpClient
+
+  beforeEach(() => {
+    _http = new httpm.HttpClient('http-client-tests', [], {keepAlive: true})
+  })
+
+  afterEach(() => {
+    _http.dispose()
+  })
+
+  it.each([true, false])('creates Agent with keepAlive %s', keepAlive => {
+    const http = new httpm.HttpClient('http-client-tests', [], {keepAlive})
+    const agent = http.getAgent('https://postman-echo.com')
+    expect(agent).toHaveProperty('keepAlive', keepAlive)
+  })
+
+  it('does basic http get request with keepAlive true', async () => {
+    const res: httpm.HttpClientResponse = await _http.get(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.url).toBe('https://postman-echo.com/get')
+  })
+
+  it('does basic head request with keepAlive true', async () => {
+    const res: httpm.HttpClientResponse = await _http.head(
+      'https://postman-echo.com/get'
+    )
+    expect(res.message.statusCode).toBe(200)
+  })
+
+  it('does basic http delete request with keepAlive true', async () => {
+    const res: httpm.HttpClientResponse = await _http.del(
+      'https://postman-echo.com/delete'
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    JSON.parse(body)
+  })
+
+  it('does basic http post request with keepAlive true', async () => {
+    const b = 'Hello World!'
+    const res: httpm.HttpClientResponse = await _http.post(
+      'https://postman-echo.com/post',
+      b
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.data).toBe(b)
+    expect(obj.url).toBe('https://postman-echo.com/post')
+  })
+
+  it('does basic http patch request with keepAlive true', async () => {
+    const b = 'Hello World!'
+    const res: httpm.HttpClientResponse = await _http.patch(
+      'https://postman-echo.com/patch',
+      b
+    )
+    expect(res.message.statusCode).toBe(200)
+    const body: string = await res.readBody()
+    const obj = JSON.parse(body)
+    expect(obj.data).toBe(b)
+    expect(obj.url).toBe('https://postman-echo.com/patch')
+  })
+
+  it('does basic http options request with keepAlive true', async () => {
+    const res: httpm.HttpClientResponse = await _http.options(
+      'https://postman-echo.com'
+    )
+    expect(res.message.statusCode).toBe(200)
+    await res.readBody()
+  })
+})