feat(integ): let a fake bind an address other than the loopback

gws, notion and github each take a --port and then hardcode 127.0.0.1.
That is right for every direct invocation and wrong inside a container:
the published port accepts the connection and then answers nothing, which
reaches the caller as an empty reply with no error anywhere explaining it.

--host leaves the default alone, so nothing that runs these on a host
changes. github also takes --advertise, because the base URL it writes
into html_url and clone_url is not always where it bound -- a container
binds 0.0.0.0, and 0.0.0.0 in a URL sends the caller nowhere.

The remaining integ servers carry the same hardcoded bind and are left
alone here.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

integ/server/github_server.py

@@ -1898,8 +1898,13 @@ def seed_state(state: FakeGitHub, repos: list[str], metadata: list[str],
         seed_commits(state, full_name, fixtures / fixture)
 
 
-async def _serve(port: int, repos: list[str], metadata: list[str],
-                 commits: list[str], create_repos: bool) -> None:
+async def _serve(port: int,
+                 repos: list[str],
+                 metadata: list[str],
+                 commits: list[str],
+                 create_repos: bool,
+                 host: str = "127.0.0.1",
+                 advertise: str | None = None) -> None:
     state = FakeGitHub()
     state.create_repos = create_repos
     state.seed = (repos, metadata, commits)
@@ -1907,9 +1912,13 @@ async def _serve(port: int, repos: list[str], metadata: list[str],
     server = GitHubServer(state)
     runner = web.AppRunner(build_app(server))
     await runner.setup()
-    site = web.TCPSite(runner, "127.0.0.1", port)
+    site = web.TCPSite(runner, host, port)
     await site.start()
-    state.base = f"http://127.0.0.1:{port}"
+    # What the fake calls itself in every html_url and clone_url it hands
+    # out, which is not always where it binds: a container binds 0.0.0.0
+    # and is reached on a published loopback port, and 0.0.0.0 in a URL
+    # sends the caller nowhere.
+    state.base = (advertise or f"http://127.0.0.1:{port}").rstrip("/")
     print(f"GITHUB_ENDPOINT={state.base}", flush=True)
     await asyncio.Event().wait()
 
@@ -1942,10 +1951,19 @@ def main() -> None:
         help="refuse POST /user/repos with 403, the way a fine-grained "
         "token without Administration:write does; fork and rename stay "
         "available")
+    parser.add_argument("--host",
+                        default="127.0.0.1",
+                        help="bind address; 0.0.0.0 in a container, where "
+                        "binding the loopback publishes a port that accepts "
+                        "the connection and then answers nothing")
+    parser.add_argument("--advertise",
+                        help="base URL to put in html_url and clone_url, "
+                        "when callers reach this fake by a name other than "
+                        "loopback (default http://127.0.0.1:<port>)")
     args = parser.parse_args()
     asyncio.run(
         _serve(args.port, args.repo, args.metadata, args.commits,
-               not args.no_create_repos))
+               not args.no_create_repos, args.host, args.advertise))
 
 
 if __name__ == "__main__":

integ/server/gws_server.ts

@@ -2915,7 +2915,7 @@ function rangeLabelFor(range: A1Range, requested: string): string {
   return `${range.tab.title}!A1:Z1000`
 }
 
-export function startServer(port: number): Promise<http.Server> {
+export function startServer(port: number, host = '127.0.0.1'): Promise<http.Server> {
   const server = http.createServer((req, res) => {
     const chunks: Buffer[] = []
     req.on('data', (chunk: Buffer) => chunks.push(chunk))
@@ -2953,7 +2953,7 @@ export function startServer(port: number): Promise<http.Server> {
     })
   })
   return new Promise((resolve) => {
-    server.listen(port, '127.0.0.1', () => resolve(server))
+    server.listen(port, host, () => resolve(server))
   })
 }
 
@@ -2961,7 +2961,12 @@ const isMain = process.argv[1] !== undefined && process.argv[1].endsWith('gws_se
 if (isMain) {
   const portArg = process.argv.indexOf('--port')
   const port = portArg !== -1 ? parseInt(process.argv[portArg + 1] as string, 10) : 19999
-  void startServer(port).then(() => {
+  // Loopback by default, which is every direct invocation. A container has
+  // to bind 0.0.0.0 or its published port accepts the connection and then
+  // answers nothing -- an empty reply with no error anywhere to explain it.
+  const hostArg = process.argv.indexOf('--host')
+  const host = hostArg !== -1 ? (process.argv[hostArg + 1] as string) : '127.0.0.1'
+  void startServer(port, host).then(() => {
     console.log(`GWS_URL=http://127.0.0.1:${String(port)}`)
   })
 }

integ/server/notion_server.ts

@@ -1693,11 +1693,11 @@ function serve(db: PrismaClient, fx: Fixture): Server {
   })
 }
 
-export async function startServer(port: number): Promise<Server> {
+export async function startServer(port: number, host = '127.0.0.1'): Promise<Server> {
   const { db, fx } = await createStore(`rest-${String(port)}`)
   const server = serve(db, fx)
   return new Promise((resolve) => {
-    server.listen(port, '127.0.0.1', () => resolve(server))
+    server.listen(port, host, () => resolve(server))
   })
 }
 
@@ -1851,7 +1851,12 @@ if (isMain) {
   const portArg = process.argv.indexOf('--port')
   const port =
     portArg !== -1 ? Number.parseInt(process.argv[portArg + 1] as string, 10) : DEFAULT_PORT
-  void startServer(port).then(() => {
+  // Loopback by default, which is every direct invocation. A container has
+  // to bind 0.0.0.0 or its published port accepts the connection and then
+  // answers nothing -- an empty reply with no error anywhere to explain it.
+  const hostArg = process.argv.indexOf('--host')
+  const host = hostArg !== -1 ? (process.argv[hostArg + 1] as string) : '127.0.0.1'
+  void startServer(port, host).then(() => {
     console.log(`NOTION_URL=http://127.0.0.1:${String(port)}`)
   })
 }