feat(prompts): implement customizable commit message prompts

- Added a new section in the UI for customizing commit message prompts.
- Integrated a system prompt for AI-generated commit messages, allowing users to define their own instructions.
- Updated the backend to merge custom prompts with default settings for commit message generation.
- Enhanced the commit message generation logic to utilize the effective system prompt based on user settings.

apps/ui/src/components/views/settings-view/prompts/prompt-customization-section.tsx

@@ -12,6 +12,7 @@ import {
   RotateCcw,
   Info,
   AlertTriangle,
+  GitCommitHorizontal,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import type { PromptCustomization, CustomPrompt } from '@automaker/types';
@@ -20,6 +21,7 @@ import {
   DEFAULT_AGENT_PROMPTS,
   DEFAULT_BACKLOG_PLAN_PROMPTS,
   DEFAULT_ENHANCEMENT_PROMPTS,
+  DEFAULT_COMMIT_MESSAGE_PROMPTS,
 } from '@automaker/prompts';
 
 interface PromptCustomizationSectionProps {
@@ -219,7 +221,7 @@ export function PromptCustomizationSection({
       {/* Tabs */}
       <div className="p-6">
         <Tabs value={activeTab} onValueChange={setActiveTab}>
-          <TabsList className="grid grid-cols-4 w-full">
+          <TabsList className="grid grid-cols-5 w-full">
             <TabsTrigger value="auto-mode" className="gap-2">
               <Bot className="w-4 h-4" />
               Auto Mode
@@ -236,6 +238,10 @@ export function PromptCustomizationSection({
               <Sparkles className="w-4 h-4" />
               Enhancement
             </TabsTrigger>
+            <TabsTrigger value="commit-message" className="gap-2">
+              <GitCommitHorizontal className="w-4 h-4" />
+              Commit
+            </TabsTrigger>
           </TabsList>
 
           {/* Auto Mode Tab */}
@@ -443,6 +449,34 @@ export function PromptCustomizationSection({
               />
             </div>
           </TabsContent>
+
+          {/* Commit Message Tab */}
+          <TabsContent value="commit-message" className="space-y-6 mt-6">
+            <div className="flex items-center justify-between mb-4">
+              <h3 className="text-sm font-medium text-foreground">Commit Message Prompts</h3>
+              <Button
+                variant="ghost"
+                size="sm"
+                onClick={() => resetToDefaults('commitMessage')}
+                className="gap-2"
+              >
+                <RotateCcw className="w-3 h-3" />
+                Reset Section
+              </Button>
+            </div>
+
+            <div className="space-y-4">
+              <PromptField
+                label="System Prompt"
+                description="Instructions for generating git commit messages from diffs. The AI will receive the git diff and generate a conventional commit message."
+                defaultValue={DEFAULT_COMMIT_MESSAGE_PROMPTS.systemPrompt}
+                customValue={promptCustomization?.commitMessage?.systemPrompt}
+                onCustomValueChange={(value) =>
+                  updatePrompt('commitMessage', 'systemPrompt', value)
+                }
+              />
+            </div>
+          </TabsContent>
         </Tabs>
       </div>
     </div>