fix(sdd): batch reviews check the diff against the brief's file list

Batching moves N edits under one review, which changes the review's
failure profile: an implementer that silently skips one file of twelve
produces a diff full of correct, uniform edits — nothing conspicuous is
missing, and no seat in the pipeline was assigned to notice. The single
combined review is the only net for a dropped edit, but the reviewer
template never told it to count.

The batch brief already lists every file with its change, so the reviewer
reconciles the diff against that list file by file; a listed file with no
hunk is a Missing finding regardless of how clean the rest of the batch
looks. Conditional on a multi-file brief, so single-task reviews are
unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skills/subagent-driven-development/task-reviewer-prompt.md

@@ -86,6 +86,12 @@ Subagent (general-purpose):
     - **Misunderstood:** right feature built the wrong way, wrong problem
       solved
 
+    If the brief lists several files each with its own change (a batched
+    dispatch), check the diff against that list file by file: every listed
+    file must have its corresponding hunk. A listed file the diff never
+    touches is a Missing finding, no matter how clean the rest of the
+    batch looks.
+
     If a requirement cannot be verified from this diff alone (it lives in
     unchanged code or spans tasks), report it as a ⚠️ item instead of
     broadening your search.