merge: 合入候选分支（09-17借款/ERP退役、09-18编号、09-19预算并发、完整10-05错误码迁移，均经确认）

# Conflicts:
#	.agents/skills/trellis-before-dev/SKILL.md
#	.agents/skills/trellis-brainstorm/SKILL.md
#	.agents/skills/trellis-continue/SKILL.md
#	.agents/skills/trellis-start/SKILL.md
#	.trellis/tasks/08-23-isolated-backup-restore-drill/design.md
#	.trellis/tasks/08-23-isolated-backup-restore-drill/prd.md
#	.trellis/tasks/09-05-error-explainability-payment-readiness/prd.md
#	.trellis/tasks/09-05-error-explainability-payment-readiness/task.json
#	.trellis/tasks/09-09-existing-deploy-seed-separation/implement.md
#	.trellis/tasks/archive/2026-09/09-05-trellis-upgrade-rule-cleanup/task.json
#	.trellis/workflow.md
#	scripts/qa/error-reason-legacy-baseline.json
#	server/src/routes/apOperations.js
#	server/src/routes/portal.js
#	server/src/routes/todos.js
#	server/tests/unit/fixtures/error-reason-messages.json
#	server/tests/unit/routes/apOperations.permissions.test.js

server/tests/unit/routes/portal.test.js

@@ -353,6 +353,19 @@ async function buildApp(options = {}) {
 }
 
 describe("portal routes", () => {
+
+  it("returns the registered disabled reason without changing the portal gate", async () => {
+    featureFlagState.portalHome = false;
+    const { app, prisma } = await buildApp();
+    try {
+      const response = await app.inject({ method: "GET", url: "/api/portal/home", headers: { authorization: "Bearer synthetic" } });
+      expect(response.statusCode).toBe(409);
+      expect(response.json().error.code).toBe("VALID_001");
+      expect(response.json().error.details).toMatchObject({ reasonCode: "portal.disabled", featureFlag: "portal_home_v1_disabled" });
+      const businessCalls = Object.entries(prisma).filter(([name]) => name !== "featureFlag").flatMap(([, model]) => Object.values(model ?? {})).filter(vi.isMockFunction);
+      expect(businessCalls.every((fn) => fn.mock.calls.length === 0)).toBe(true);
+    } finally { await app.close(); }
+  });
   beforeEach(() => {
     vi.useFakeTimers();
     vi.setSystemTime(new Date("2026-04-12T02:00:00.000Z"));