feat(FN-4074): add priority option to task creation in engine and extension

Adds task priority support to the task creation flow, spanning the engine runtime (`agent-tools.ts`, `triage.ts`), the CLI extension interface (`extension.ts`), and corresponding documentation and tests. The changeset bumps `@runfusion/fusion` as a minor version.

Fusion-Task-Id: FN-4074

Fusion-Task-Lineage: 726c0ae6-90fb-4c13-ace1-215a2becb2a9

packages/engine/src/agent-tools.ts

@@ -26,11 +26,18 @@ import { computeApprovalDedupeKey } from "./agent-action-gate.js";
 
 // ── Tool parameter schemas (canonical definitions) ────────────────────────
 
+const TASK_CREATE_PRIORITY_VALUES = ["low", "normal", "high", "urgent"] as const;
+
 export const taskCreateParams = Type.Object({
   description: Type.String({ description: "What needs to be done" }),
   dependencies: Type.Optional(
     Type.Array(Type.String(), { description: "Task IDs this new task depends on (e.g. [\"KB-001\"])" }),
   ),
+  priority: Type.Optional(
+    Type.Union(TASK_CREATE_PRIORITY_VALUES.map((priority) => Type.Literal(priority)), {
+      description: "Task priority (low, normal, high, urgent)",
+    }),
+  ),
 });
 
 export const taskLogParams = Type.Object({
@@ -628,6 +635,7 @@ export function createTaskCreateTool(
           description: params.description,
           dependencies: params.dependencies,
           column: "triage",
+          priority: params.priority,
           source: provenance ? {
             sourceType: provenance.sourceType,
             sourceAgentId: provenance.sourceAgentId,