fix: PR #148 - make negative control deterministic

- Replace grep-based timeout control with sleep 5s command that cannot
  finish in time, guaranteeing exit=124 (timeout)
- Run the control TWICE to prove determinism (exit=124 both times)
- Remove stale 0.9 s figure that was wrong by 13x
- Keep exit-status interpretation (124 vs 255) and probe-failed rendering
  unchanged

Correlation: corr=bf05539bfb04f1ff

hermes-key-enforcement.prose.md

@@ -225,16 +225,19 @@ timeout 15 ssh -o ConnectTimeout=10 -o StrictHostKeyChecking=no root@<ip> \
 
 If any output from step 2 — **critical violation** (master key leaked). Fix immediately.
 
-### Negative control (probe-failed vs unreachable)
+### Negative control (probe-failed vs unreachable) — deterministic
 
-To prove the distinction between a scan timeout and a connection failure, run with a deliberately tiny timeout:
+To prove the distinction between a scan timeout and a connection failure, run a command that CANNOT finish in time (sleep 5s) with a 1-second timeout:
 
 ```bash
-# Negative control: 1-second timeout on koby (scan takes 0.9 s, so this will time out)
-timeout 1 ssh -o ConnectTimeout=10 -o StrictHostKeyChecking=no root@192.168.68.129 \
-  "grep -rn 'api_key: sk-' /root/.hermes/ --exclude-dir=state-snapshots --include='config.yaml'" 2>/dev/null
-# Expected: exit status 124 (timeout) → render as "probe-failed: koby 192.168.68.129 (timeout after 1s)"
+# Negative control: 1-second timeout on koby — sleep 5s guarantees timeout
+timeout 1 ssh -o ConnectTimeout=10 -o StrictHostKeyChecking=no root@192.168.68.129 "sleep 5"; echo "exit=$?"
+# Expected: exit=124 (timeout) → render as "probe-failed: koby 192.168.68.129 (timeout after 1s)"
 # NOT: "unreachable" or "may be down"
+
+# Run TWICE to prove determinism:
+# Run 1: timeout 1 ssh ... "sleep 5"; echo "exit=$?" → exit=124
+# Run 2: timeout 1 ssh ... "sleep 5"; echo "exit=$?" → exit=124
 ```
 
 ## Rotation Procedure