feat(FN-1524): add POST /routines/:id/trigger endpoint

- Add POST /routines/:id/trigger as canonical endpoint for manual routine triggers
- Keep POST /routines/:id/run as backward-compatible alias
- Remove duplicate recordRun calls from routine route handlers (persistence handled by RoutineRunner)
- Update webhook auth to return 401 instead of 403 for signature failures
- Fix TypeScript types for promptOverrides to support null values (delete semantics)
- Fix API endpoint to return empty diff stats when worktree doesn't exist

packages/dashboard/src/agent-generation.ts

@@ -15,9 +15,9 @@
 import { randomUUID } from "node:crypto";
 
 // Dynamic import for @fusion/core to get prompt override resolution
- 
-type PromptOverrideMap = Record<string, string | undefined>;
- 
+
+type PromptOverrideMap = Record<string, string | null>;
+
 type ResolvePromptFn = (key: string, overrides?: PromptOverrideMap) => string;
 let resolvePrompt: ResolvePromptFn = () => "";
 let promptCatalogReady = false;
@@ -414,7 +414,7 @@ export function parseGenerationResponse(text: string): AgentGenerationSpec {
  *
  * @param ip - Client IP for rate limiting
  * @param roleDescription - The user's description of the desired agent role
- * @returns Session object (without spec — call generateAgentSpec to populate)
+ * @returns Session object (without spec - call generateAgentSpec to populate)
  */
 export async function startAgentGeneration(
   ip: string,

packages/dashboard/src/routes.ts

@@ -116,15 +116,15 @@ export function __setCreateKbAgentForRefine(mock: typeof createKbAgentForRefine)
 }
 
 // Default system prompt for workflow step refinement (fallback when overrides unavailable)
- 
-let resolveWorkflowStepRefinePrompt: (key: string, overrides?: Record<string, string | undefined>) => string = () => DEFAULT_WORKFLOW_STEP_REFINE_PROMPT;
+
+let resolveWorkflowStepRefinePrompt: (key: string, overrides?: Record<string, string | null>) => string = () => DEFAULT_WORKFLOW_STEP_REFINE_PROMPT;
 let promptOverridesReady = false;
 
 async function initPromptOverrides() {
   if (promptOverridesReady) return;
   try {
     const core = await import("@fusion/core");
-    resolveWorkflowStepRefinePrompt = (key: string, overrides?: Record<string, string | undefined>) =>
+    resolveWorkflowStepRefinePrompt = (key: string, overrides?: Record<string, string | null>) =>
       core.resolvePrompt(key as keyof typeof core.PROMPT_KEY_CATALOG, overrides);
     promptOverridesReady = true;
   } catch {