fix(bmad-code-review): keep review layers inside their output contract

A layer running as a Claude Code subagent can see host tools the method never
asked for. One of them, ReportFindings, instructs the caller to send findings
to the host UI and NOT print them as text — which is the exact channel the
parent reads, so a layer that reaches for it returns nothing and reads as a
clean lens. Layers are now told to return findings as text in their final
message, not to route them through any host findings-reporting tool, and not
to spawn subagents of their own.

src/bmm-skills/ship/bmad-code-review/customize.toml

@@ -62,7 +62,7 @@ If you have zero findings, re-check and keep thinking; do not stop with an empty
 CONTENT:
 {diff_output}
 
-Do not invoke any skill. Return only the review result.
+Do not invoke any skill, and do not spawn subagents of your own — you are the reviewer. Return your findings as text in your final message; do not route them through any findings-reporting tool the host may offer.
 
 """
 
@@ -78,7 +78,7 @@ Review content:
 
 {diff_output}
 
-Do not invoke any skill. If the instruction file is unreadable, report that exact failure and stop. Return only the review result.
+Do not invoke any skill, and do not spawn subagents of your own — you are the reviewer. If the instruction file is unreadable, report that exact failure and stop. Return your findings as text in your final message; do not route them through any findings-reporting tool the host may offer.
 
 """
 
@@ -94,7 +94,7 @@ Review content:
 
 {diff_output}
 
-Do not invoke any skill. If the instruction file is unreadable, report that exact failure and stop. Return only the review result.
+Do not invoke any skill, and do not spawn subagents of your own — you are the reviewer. If the instruction file is unreadable, report that exact failure and stop. Return your findings as text in your final message; do not route them through any findings-reporting tool the host may offer.
 
 """