fix(vfs): forward the typed snapshot through the branch payload builder

The branch buildPayload implementations hand-list the params they pass to
buildCopilotRequestPayload and forwarded workspaceContext but dropped vfs, so the
typed snapshot never reached the Go request (req.Vfs was always nil and the
append-only delta path never engaged). Forward vfs in both the workflow and
workspace branches, and add a regression guard asserting the branch threads it
through (the bug slipped past tests because post.test mocked the payload builder
and payload.test called it directly, bypassing the branch).

Author: Sg312

apps/sim/lib/copilot/chat/post.test.ts

@@ -144,7 +144,7 @@ describe('handleUnifiedChatPost', () => {
     getEffectiveDecryptedEnv.mockResolvedValue({ API_KEY: 'secret' })
     generateWorkspaceSnapshot.mockResolvedValue({
       markdown: 'workspace context',
-      snapshot: undefined,
+      snapshot: { workflows: [{ id: 'wf-1', name: 'Alpha', path: 'workflows/Alpha' }] },
     })
     processContextsServer.mockResolvedValue([])
     resolveActiveResourceContext.mockResolvedValue(null)
@@ -186,6 +186,8 @@ describe('handleUnifiedChatPost', () => {
       expect.objectContaining({
         model: 'claude-opus-4-8',
         workspaceContext: 'workspace context',
+        // Regression guard: the branch must forward the typed snapshot, not drop it.
+        vfs: expect.objectContaining({ workflows: expect.any(Array) }),
       }),
       { selectedModel: 'claude-opus-4-8' }
     )
@@ -224,6 +226,8 @@ describe('handleUnifiedChatPost', () => {
       expect.objectContaining({
         workspaceId: 'ws-1',
         workspaceContext: 'workspace context',
+        // Regression guard: the branch must forward the typed snapshot, not drop it.
+        vfs: expect.objectContaining({ workflows: expect.any(Array) }),
       }),
       { selectedModel: '' }
     )

apps/sim/lib/copilot/chat/post.ts

@@ -619,6 +619,7 @@ async function resolveBranch(params: {
             prefetch: payloadParams.prefetch,
             implicitFeedback: payloadParams.implicitFeedback,
             workspaceContext: payloadParams.workspaceContext,
+            vfs: payloadParams.vfs,
             userPermission: payloadParams.userPermission,
             userTimezone: payloadParams.userTimezone,
             userMetadata: payloadParams.userMetadata,
@@ -678,6 +679,7 @@ async function resolveBranch(params: {
           fileAttachments: payloadParams.fileAttachments,
           chatId: payloadParams.chatId,
           workspaceContext: payloadParams.workspaceContext,
+          vfs: payloadParams.vfs,
           userPermission: payloadParams.userPermission,
           userTimezone: payloadParams.userTimezone,
           userMetadata: payloadParams.userMetadata,