Clarify review prompts should not run builds or tests (#472)

## Summary
- add explicit review-template instructions for Codex, Claude Code, and
Gemini not to build projects, run tests, or execute code during review
- keep the guidance scoped to review prompts by updating the
agent-specific review templates
- update prompt template tests to assert the new instruction

Closes #311

Author: wesm

internal/prompt/templates/claude-code_review.tmpl

@@ -1,6 +1,7 @@
 You are a code reviewer. Review the code changes shown below.
 
 Return only the final review. Do NOT narrate your process, mention files you opened, or describe intermediate checks.
+Do NOT build the project, run the test suite, or execute the code while reviewing. Base your review on the diff and static analysis only.
 
 ## Output Format
 

internal/prompt/templates/codex_review.tmpl

@@ -1,6 +1,7 @@
 You are a code reviewer. Review the code changes shown below.
 
 Return only the final review. Do NOT narrate your process, mention files you opened, or describe intermediate checks.
+Do NOT build the project, run the test suite, or execute the code while reviewing. Base your review on the diff and static analysis only.
 
 ## Output Format
 

internal/prompt/templates/gemini_review.tmpl

@@ -1,6 +1,7 @@
 You are a code reviewer. Review the code changes shown below.
 
 Your goal is to be extremely concise and professional. Do NOT explain your process or list the steps you are taking. Just provide the final review results.
+Do NOT build the project, run the test suite, or execute the code while reviewing. Base your review on the diff and static analysis only.
 
 ## Output Format
 

internal/prompt/templates_test.go

@@ -77,21 +77,21 @@ func TestGetSystemPrompt_Fallbacks(t *testing.T) {
 			name:           "Codex Review",
 			agent:          "codex",
 			command:        "review",
-			wantContains:   []string{"## Review Findings", "Do not include any front matter"},
+			wantContains:   []string{"## Review Findings", "Do not include any front matter", "Do NOT build the project, run the test suite, or execute the code while reviewing."},
 			wantNotDefault: true,
 		},
 		{
 			name:           "Claude Review",
 			agent:          "claude-code",
 			command:        "review",
-			wantContains:   []string{"## Review Findings", "Do not include any front matter"},
+			wantContains:   []string{"## Review Findings", "Do not include any front matter", "Do NOT build the project, run the test suite, or execute the code while reviewing."},
 			wantNotDefault: true,
 		},
 		{
 			name:           "Gemini Review",
 			agent:          "gemini",
 			command:        "review",
-			wantContains:   []string{"Do NOT explain your process"},
+			wantContains:   []string{"Do NOT explain your process", "Do NOT build the project, run the test suite, or execute the code while reviewing."},
 			wantNotDefault: true,
 		},
 		{