fix(service): start the Windows service after granting it its config (D157)

`sc start` ran inside registration, before `grant_service_access` let the
new virtual account read `sidecar.toml` — which `protect_config` had
locked to SYSTEM and Administrators. The first start died on "Access is
denied (os error 5)" and the service sat STOPPED: the SCM's
restart-on-failure policy never fires for a clean exit with an error
code. A later manual start worked, because by then the grant existed.

Found on the phase 18 walk (step 4, one Rust instance under the SCM),
from the sidecar's own log. The code is shared, so the released ServUO
installer has the same first-start failure; the org lead chose to fix
both here (D157).

Registration no longer starts the service; a new `start_registered`
runs after the grant and refreshes the reported state. A no-op on Linux,
where the service user exists before the config and registration starts
the unit itself.

Walked (Windows, elevated): install -> START_PENDING/running, /health on
the first probe, clean stop and restart, doctor clean, uninstall clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

src/rustgame/install.rs

@@ -624,7 +624,7 @@ fn deploy_instance(
         prepared.user.as_deref(),
         layout.relocated,
     )?;
-    let outcome = service::register_rust(
+    let mut outcome = service::register_rust(
         prepared,
         layout,
         &plan.id,
@@ -632,6 +632,7 @@ fn deploy_instance(
         binary_changed,
     )?;
     service::grant_service_access(&plan.config_path, &data_dir, &outcome)?;
+    service::start_registered(&mut outcome, &layout.rust_sidecar_bin, &plan.config_path)?;
     let service_record = match &outcome {
         service::Outcome::Registered {
             kind,