feat(server,web,core): explicit proxy address setting (no env vars needed) (#233)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/desktop/src/os-proxy.ts

@@ -1,11 +1,15 @@
 /**
- * OS-proxy resolution for the embedded server (design § "出网与系统代理"): on the
- * desktop, "system proxy" means the real operating-system setting. The shell resolves
+ * OS-proxy resolution for the embedded server: on the desktop, "system proxy" means
+ * the real operating-system setting. The shell resolves
  * it through Electron's resolveProxy when forking the server and injects the result
  * into the child environment as HTTP_PROXY / HTTPS_PROXY — the server's dispatcher
- * (and, while the admin switch is on, agent commands) then honor it. Variables already
- * present in the shell's environment are never overridden (same idiom as
- * bundledShellEnv): an explicitly configured environment wins over the OS lookup.
+ * (while the admin app-proxy switch is on) and agent commands (while the agent-proxy
+ * switch is on) then honor it. Variables already present in the shell's environment are
+ * never overridden (same idiom as bundledShellEnv): an explicitly configured
+ * environment wins over the OS lookup. An admin-configured explicit proxy address
+ * (server_settings `proxyUrl`) in turn wins over BOTH at the server's dispatcher and in
+ * agent command env injection — what this module injects is only the "follow the system
+ * proxy" default the server falls back to.
  *
  * Only the entry point touches Electron, behind a dynamic import; the parsing and the
  * override check stay pure so they unit-test without an Electron runtime.