Convert curly to square brackets in code-reviewer.md placeholders

Matches the style used by the spec-reviewer-prompt.md and
code-quality-reviewer-prompt.md call sites, which already use square
brackets ([VAR] or [VAR — description]). No semantic change — these
placeholders are filled in by the controller; nothing programmatic
substitutes them.

skills/requesting-code-review/code-reviewer.md

@@ -14,25 +14,25 @@ Subagent (general-purpose):
 
     ## What Was Implemented
 
-    {DESCRIPTION}
+    [DESCRIPTION]
 
     ## Requirements / Plan
 
-    {PLAN_OR_REQUIREMENTS}
+    [PLAN_OR_REQUIREMENTS]
 
     ## Git Range to Review
 
-    **Base:** {BASE_SHA}
-    **Head:** {HEAD_SHA}
+    **Base:** [BASE_SHA]
+    **Head:** [HEAD_SHA]
 
     ```bash
-    git diff --stat {BASE_SHA}..{HEAD_SHA}
-    git diff {BASE_SHA}..{HEAD_SHA}
+    git diff --stat [BASE_SHA]..[HEAD_SHA]
+    git diff [BASE_SHA]..[HEAD_SHA]
     ```
 
     ## Read-Only Review
 
-    Your review is read-only on this checkout. Do not mutate the working tree, the index, HEAD, or branch state in any way. Use tools like `git show`, `git diff`, and `git log` to inspect history. If you need a working copy of a different revision, check it out into a separate temporary directory (e.g. `git worktree add /tmp/review-{SHA} {SHA}`) — never move HEAD on this checkout.
+    Your review is read-only on this checkout. Do not mutate the working tree, the index, HEAD, or branch state in any way. Use tools like `git show`, `git diff`, and `git log` to inspect history. If you need a working copy of a different revision, check it out into a separate temporary directory (e.g. `git worktree add /tmp/review-[SHA] [SHA]`) — never move HEAD on this checkout.
 
     ## What to Check
 
@@ -126,10 +126,10 @@ Subagent (general-purpose):
 ```
 
 **Placeholders:**
-- `{DESCRIPTION}` — brief summary of what was built
-- `{PLAN_OR_REQUIREMENTS}` — what it should do (plan file path, task text, or requirements)
-- `{BASE_SHA}` — starting commit
-- `{HEAD_SHA}` — ending commit
+- `[DESCRIPTION]` — brief summary of what was built
+- `[PLAN_OR_REQUIREMENTS]` — what it should do (plan file path, task text, or requirements)
+- `[BASE_SHA]` — starting commit
+- `[HEAD_SHA]` — ending commit
 
 **Reviewer returns:** Strengths, Issues (Critical / Important / Minor), Recommendations, Assessment