Install sets a default LOG_FILE in the env file on Windows (no console as a service)

SPEC.md

@@ -186,8 +186,13 @@ By default install creates the canonical layout and copies the binary into
 it (Windows: `%ProgramFiles%\gpu-turnstile\`, plus
 `%ProgramData%\gpu-turnstile\` for logs; Linux: `/var/lib/gpu-turnstile/`
 with the config at `/etc/gpu-turnstile.env`). An existing config in the
-target location is never overwritten. `--no-copy` registers the current
-executable location as-is instead.
+target location is never overwritten. On Windows the install also makes
+sure the env file sets `LOG_FILE` to
+`%ProgramData%\gpu-turnstile\gpu-turnstile.log` (appended only when no
+`LOG_FILE=` line exists) since a service has no console; on Linux logs go
+to the journal via stderr, so no default is set there. `--no-copy`
+registers the current executable location as-is and leaves the config
+untouched.
 
 ### Windows
 
@@ -195,8 +200,9 @@ executable location as-is instead.
   `%ProgramData%\gpu-turnstile\`, copies the exe and (if none exists there
   yet) the `gpu-turnstile.env` into the Program Files directory, and
   registers that copy as a Windows service; recovery actions restart it
-  5 s after any failure. Logs go to the ProgramData directory via
-  `LOG_FILE` since there is no console.
+  5 s after any failure. The install ensures the env file sets `LOG_FILE`
+  to `%ProgramData%\gpu-turnstile\gpu-turnstile.log` since there is no
+  console — an existing `LOG_FILE` setting is kept.
 - **Account**: the service always runs as the virtual account
   `NT SERVICE\gpu-turnstile` — a per-service low-privilege identity the
   SCM manages (no password, automatic logon-as-a-service right, no admin