fix(conformance): chainsaw checks use contains(), not unsupported =~

Every chainsaw `check` used the regex operator `=~` (`($stdout =~ 'X'): true`),
which chainsaw's expression engine rejects ('SyntaxError: Unknown char: ~') — so
EVERY such test failed on the assertion even when the behavior passed. Proven with
data-survival (R-STATE-01): the Longhorn canary genuinely SURVIVED pod destruction
(DATA_SURVIVED_OK) but the test FAILED on the `=~` syntax. Converted all 10 tests to
JMESPath `contains($stdout, 'X')` (data-survival's alternation → contains||contains).
data-survival now PASSES; the other 9 (later-phase components) are syntactically fixed
for when their phases deploy.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

conformance/tests/l2-behavioral/sso-forward-auth/chainsaw-test.yaml

@@ -37,7 +37,7 @@ spec:
                 curl -s -o /dev/null -w '%{http_code}' https://<service>.home.keithjackson.dev)
               echo "unauth_code=$code"
               case "$code" in 302|303|401|403) echo CHALLENGED_OK ;; *) exit 1 ;; esac
-            check: { ($stdout =~ 'CHALLENGED_OK'): true }
+            check: { (contains($stdout, 'CHALLENGED_OK')): true }
     - name: then-authenticated-is-granted
       try:
         - script: