qa(diag): gate spawn/input setup logs behind gigline.SetupLogs cvar (default off)

TODO item: remove/gate the TEMP QA diagnostics. The GigLine SIM/GROUND probes
were already removed (PR #8); what remained was the settle-timer log and the
GigLine IN: input-setup logs. Now gated behind a TAutoConsoleVariable
(gigline.SetupLogs, default 0 in DefaultEngine.ini [ConsoleVariables]), so a
shipped build's log has no setup spam; re-enable at runtime with
'gigline.SetupLogs 1'. The -qaselftest QA logs are a deliberate release-check
feature (Docs/release-checks.md) and stay ungated. Verified on the packaged
build: 0 setup-log lines, QA suite still all PASS.

Game/GigLine/Config/DefaultEngine.ini

@@ -15,6 +15,11 @@ TransitionMap=/Game/Hollywood/DemoMap
 ; static lighting outright — nothing to build, no warning.
 r.AllowStaticLighting=False
 
+[ConsoleVariables]
+; Dev diagnostics (spawn/input setup logs) are off by default in shipped builds.
+; Re-enable at runtime: `gigline.SetupLogs 1`.
+gigline.SetupLogs=0
+
 [URL]
 GameName=GigLine