refactor(ai): consolidate ai operation types and reduce duplication

Refactor AI service layer to reduce code duplication and improve consistency.

Changes:
- Rename AIOperationRequest to OperationRequest for consistency
- Extract shared logic for issue-targeted operations (respond, triage) into triggerIssueAIOp helper
- Standardize field alignment in struct definitions
- Remove redundant error handling patterns

This reduces the API operations file by ~40 lines while maintaining identical functionality.

modules/ai/types.go

@@ -207,11 +207,11 @@ type GenerateIssueResponseRequest struct {
 
 // GenerateIssueResponseResponse is the response from generating an issue response
 type GenerateIssueResponseResponse struct {
-	Response            string   `json:"response"`
-	FollowUpQuestions   []string `json:"follow_up_questions,omitempty"`
-	Confidence          float64  `json:"confidence"`
-	InputTokens         int      `json:"input_tokens"`
-	OutputTokens        int      `json:"output_tokens"`
+	Response          string   `json:"response"`
+	FollowUpQuestions []string `json:"follow_up_questions,omitempty"`
+	Confidence        float64  `json:"confidence"`
+	InputTokens       int      `json:"input_tokens"`
+	OutputTokens      int      `json:"output_tokens"`
 }
 
 // HealthCheckResponse is the response from a health check

modules/errors/codes.go

@@ -172,11 +172,11 @@ const (
 
 // AI errors (AI_)
 const (
-	AIDisabled         ErrorCode = "AI_DISABLED"
-	AIUnitNotEnabled   ErrorCode = "AI_UNIT_NOT_ENABLED"
+	AIDisabled          ErrorCode = "AI_DISABLED"
+	AIUnitNotEnabled    ErrorCode = "AI_UNIT_NOT_ENABLED"
 	AIOperationNotFound ErrorCode = "AI_OPERATION_NOT_FOUND"
 	AIRateLimitExceeded ErrorCode = "AI_RATE_LIMIT_EXCEEDED"
-	AIServiceError     ErrorCode = "AI_SERVICE_ERROR"
+	AIServiceError      ErrorCode = "AI_SERVICE_ERROR"
 	AIOperationDisabled ErrorCode = "AI_OPERATION_DISABLED"
 )