bugfix: block approval when rendered diff output is reformatted

Author: cowwoc

.cat/issues/v2/v2.1/block-approval-gate-without-diff/index.json

@@ -1,7 +1,5 @@
 {
   "status": "closed",
   "resolution": "implemented",
-  "dependencies": [],
-  "blocks": [],
   "target_branch": "v2.1"
 }

client/src/main/java/io/github/cowwoc/cat/hooks/ask/WarnApprovalWithoutRenderDiff.java

@@ -31,8 +31,7 @@
  * from blocking because those workflows do not change the working tree.
  * <p>
  * When cat:get-diff was invoked but the output appears reformatted (sparse box characters
- * with many manual diff signs), the handler issues a warning via additional context
- * rather than blocking.
+ * with many manual diff signs), the handler blocks the approval gate.
  */
 public final class WarnApprovalWithoutRenderDiff implements AskHandler
 {
@@ -135,7 +134,7 @@ private Result checkSessionForGetDiff(Path sessionFile)
           DO NOT extract into code blocks or reformat as standard diff.
 
           The user must see the actual 4-column table output.""";
-        return Result.withContext(warning);
+        return Result.block(warning);
       }
     }
     catch (IOException e)

client/src/test/java/io/github/cowwoc/cat/hooks/test/WarnApprovalWithoutRenderDiffTest.java

@@ -246,13 +246,13 @@ public void presentGetDiffWithBoxCharsAllows() throws IOException
   }
 
   /**
-   * Verifies that the sparse box character warning triggers when "get-diff" is present
+   * Verifies that the sparse box character check blocks approval when "get-diff" is present
    * but box characters are insufficient and manual diff signs are present.
    *
    * @throws IOException if test setup fails
    */
   @Test
-  public void getDiffPresentButSparseBoxCharsTriggersReformatWarning() throws IOException
+  public void getDiffPresentButSparseBoxCharsBlocksApproval() throws IOException
   {
     Path tempDir = Files.createTempDirectory("test-warn-approval-");
     try (TestClaudeHook scope = new TestClaudeHook(tempDir, tempDir, tempDir))
@@ -288,7 +288,7 @@ public void getDiffPresentButSparseBoxCharsTriggersReformatWarning() throws IOEx
 
       AskHandler.Result result = handler.check(toolInput, sessionId);
 
-      requireThat(result.additionalContext(), "additionalContext").contains("RENDER-DIFF OUTPUT MAY BE REFORMATTED");
+      requireThat(result.blocked(), "blocked").isTrue();
     }
     finally
     {