fix(browser): change default port to 23315

[hi-ogawa]

• closes Pick lower ephemeral port for browser mode #9035

Browser mode's default port 63315 can be reserved by Windows when Hyper-V, WSL2, or Docker Desktop is running, for example 63272-63371 on this issue. Binding a reserved port fails with EACCES (voidzero-dev/vite-task#838, facebook/lexical#8673), but Vite only falls back to the next port on EADDRINUSE (vite http.ts), so the run fails. This PR changes the default to 23315, chosen as described below.

Port choice research

The new port, and the ports after it that additional browser projects take, stay clear of:

• Windows' dynamic port range, 49152-65535 by default (Microsoft Learn). Windows reserves blocks out of this range, and the blocks change on every reboot (docker/for-win#3171). Machines where the range was changed to start lower can still hit a reserved block (docker/for-win#3171), and api: { port: 0 } from fix: support api.port 0 #11641 covers them.
• Linux's default ephemeral range, 32768-60999 (kernel docs, ip_local_port_range), where an outbound connection can briefly hold the port and push Vite to the next one, as this repo's own browser tests have run into (server-url fixture).
• the ports browsers refuse to load, such as 5060, 6000, 6665-6669, and 10080 (Fetch Standard, bad ports).
• ports with a known use, such as the default ports of Vite (5173, Vite docs) and the Vitest UI (51204, Vitest docs), so they can run side by side. 23315-23318 are unassigned in the IANA registry, and searching public code on GitHub for forms such as localhost:23315, port: 23315, or PORT=23315 finds only incidental uses, such as ports Visual Studio assigned at random to ASP.NET projects, and no tool that uses it as a default. For comparison, 8315 is the example remote-debugging-port in Electron's docs and is widely used for debugging Electron apps (GitHub search).

Among the ports that meet these, 23315 differs from 63315 by only the first digit, so it is easy to recognize as the new default.

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