Clarify FEX wrapper runtime dependency

docs/evidence/v0454-candidate-2026-10-28.md

@@ -22,6 +22,17 @@ smoke title directories or owned test processes. It did not wake the Frame or
 send input. Nobody confirmed wearing the Frame, so no wearer-visible or
 physical-controller result follows.
 
+Follow-up probes at about 22:40–22:45 UTC each acquired a new unique owner in
+the shared headset lock before reading status. SteamVR stayed at activity 3
+(standby), proximity was 2.3125–2.375 and battery was 100%. A bounded,
+read-only `FEXBash --help` probe reported that `SteamLinuxRuntime_4` did not
+exist in Steam's common directory. A separate read of `/usr/bin/FEXBash` found
+that its wrapper exits when that directory is absent. The probes did not
+install a runtime, launch a title, wake the headset or send input. Each owner
+released its lock. The available FEX wrapper therefore did not provide an
+immediate x86 Linux launch path; this does not establish that every possible
+runtime source is absent.
+
 **Release decision: hold v0.4.54.** The smoke script at the candidate commit
 returned exit 0 even though it recorded a skipped launch. Under the current
 release rule, a skip cannot satisfy the smoke gate. The accompanying change