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/SKILL.md

@@ -193,6 +193,14 @@ that implementer. Single-file mechanical fixes also take the cheapest tier.
 
 ## The Task Loop
 
+**Batch small same-shape work.** When the plan lists several tasks that are
+each a small, independent edit of the same kind — the same one-line fix,
+constant change, or field addition repeated across files — do not dispatch
+one subagent per task. Compose ONE dispatch brief listing every file and
+its change, send the whole batch to a single subagent, and review its diff
+as one unit. Reserve one-dispatch-per-task for work that needs its own
+judgment, its own tests, or its own review surface.
+
 Everything you paste into a dispatch prompt — and everything a subagent
 prints back — stays resident in your context for the rest of the session
 and is re-read on every later turn. Hand artifacts over as files.

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.