Fix graceful shutdown hanging and killing in-flight requests

[kksingh000]

When an Application was listening with an AbortSignal and that signal was aborted while requests were in flight, two problems occurred:

1. listen() never resolved. Server#listen() in http_server_native.ts never closed the ReadableStream's controller when the underlying Deno.serve() instance shut down, so the for await loop consuming that stream in Application#listen() hung forever even after all in-flight requests had been handled.

2. In-flight requests were killed instead of completing. Server#listen() passed signal directly into Deno.serve()'s own options, which causes Deno's engine to hard-abort in-flight connections immediately on signal abort. It also registered its own abort listener that called this.close() (and therefore httpServer.shutdown()) straight away, racing Application#listen()'s own careful tracking of in-flight requests (state.handling), which already defers calling Server#close() until those requests have drained.

Fix both by:

• Closing the stream's controller once Deno.serve()'s own .finished promise resolves, so the consuming for await loop (and therefore the top-level listen() promise) terminates correctly.
• No longer passing signal into Deno.serve()'s own options, and removing Server#listen()'s own abort-triggered call to close(). Application#listen() already owns the correct abort-then-drain- then-close sequencing; Server no longer races it.

Fixes #611

Claude-Session: https://claude.ai/code/session_0126cmS4qpPbYhiSmnHo3cUo