[Trivial] clarify strict-mode warning error wording (#6916)

## Changes

Clarify that `bundle validate --strict` treats warnings as errors.
Update the acceptance snapshots.

## Why

Matches the existing `--strict` help and [Clang's
wording](https://clang.llvm.org/docs/UsersManual.html#clang-cl) for the
same behavior.

## Tests

Targeted acceptance cases, `./task checks`, and CI pass.

_This PR was written by Codex._

Author: lennartkats-db

acceptance/bundle/validate/secret_scope_invalid_permission_level/output.txt

@@ -28,4 +28,4 @@ Workspace:
   Path: /Workspace/Users/[USERNAME]/.bundle/test-bundle/default
 
 Found 2 warnings
-Error: 2 warnings were found. Warnings are not allowed in strict mode
+Error: 2 warnings were found. Warnings are treated as errors in strict mode

acceptance/bundle/validate/strict/output.txt

@@ -24,7 +24,7 @@ Workspace:
   Path: /Workspace/Users/[USERNAME]/.bundle/test-bundle/foo
 
 Found 1 warning
-Error: 1 warning was found. Warnings are not allowed in strict mode
+Error: 1 warning was found. Warnings are treated as errors in strict mode
 
 Exit code: 1
 
@@ -44,6 +44,6 @@ Workspace:
   Path: /Workspace/Users/[USERNAME]/.bundle/test-bundle/bar
 
 Found 2 warnings
-Error: 2 warnings were found. Warnings are not allowed in strict mode
+Error: 2 warnings were found. Warnings are treated as errors in strict mode
 
 Exit code: 1

cmd/bundle/validate.go

@@ -97,7 +97,7 @@ Please run this command before deploying to ensure configuration quality.`,
 			} else {
 				prefix = fmt.Sprintf("%d warnings were found", numWarnings)
 			}
-			return fmt.Errorf("%s. Warnings are not allowed in strict mode", prefix)
+			return fmt.Errorf("%s. Warnings are treated as errors in strict mode", prefix)
 		}
 
 		return err