refactor(dashboards): store dashboards as workspace files

Dashboards are now ordinary workspace files, handled like Sim pages, instead
of a separate resource. Creating or uploading `<Name>.dashboard` drops the
suffix and stamps `text/x-sim-dashboard`; the type is sticky across content
writes. The file viewer renders it live behind the `dashboards` flag, and the
public share viewer shows a workspace-only notice.

- Remove the dashboard resource: sidebar page, API routes, hooks, contracts,
  application layer, Mothership dashboards/dashboard_folders tools, resource
  tags, and the per-turn dashboardsEnabled payload.
- Revert the file discovery column (0385) and drop the dashboard folder
  resource enum (0384); dashboards never shipped, so no backfill.
- Chat panel decides previewability and tab/picker icons from the file type,
  not the name, so extensionless dashboards render and get the chart icon.
- Renderer: authored left label columns are kept intact, horizontal bar
  frames grow with row count, and hovered rows get a label-and-bar highlight.
- Simplify the create-dashboard skill around one validated example.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S6aTRnkiu7PxYZPNPXYEMV

Author: TheodoreSpeaks

apps/sim/app/api/files/uploads/finalizers.ts

@@ -22,7 +22,6 @@ import {
 import { getWorkspaceFileSize, type StorageContext } from '@/lib/uploads/shared/types'
 import { UploadSessionError, type UploadSessionRecord } from '@/lib/uploads/upload-session/service'
 import { readWorkspaceFileUploadProvenance } from '@/lib/uploads/upload-session/workspace-file-provenance'
-import { defaultFileDiscovery } from '@/lib/workspace-files/discovery'
 import { toV2File } from '@/app/api/v2/files/utils'
 
 export interface UploadActor {
@@ -377,7 +376,6 @@ async function insertOrLoadFileMetadata(
       userId: input.userId,
       workspaceId: input.workspaceId,
       context: input.context,
-      discovery: defaultFileDiscovery(input.context),
       originalName: input.originalName,
       displayName: input.originalName,
       contentType: input.contentType,

apps/sim/app/api/workspaces/[id]/dashboards/[dashboardId]/route.ts

@@ -1,5 +1,5 @@
 import type { ComponentType } from 'react'
-import { ChartColumn, Database, File as FileIcon, Table as TableIcon } from '@sim/emcn/icons'
+import { Database, File as FileIcon, Table as TableIcon } from '@sim/emcn/icons'
 import type { FolderResourceType } from '@/lib/api/contracts/folders'
 import { folderListHref } from '@/app/workspace/[workspaceId]/components/folders/search-params'
 
@@ -10,7 +10,7 @@ import { folderListHref } from '@/app/workspace/[workspaceId]/components/folders
  */
 export type FolderedHeaderResourceType = Extract<
   FolderResourceType,
-  'file' | 'knowledge_base' | 'table' | 'dashboard'
+  'file' | 'knowledge_base' | 'table'
 >
 
 export interface FolderedResourceHeaderMeta {
@@ -36,7 +36,6 @@ export const FOLDERED_RESOURCE_HEADERS: Record<
   file: { rootLabel: 'Files', rootIcon: FileIcon, listSegment: 'files' },
   knowledge_base: { rootLabel: 'Knowledge bases', rootIcon: Database, listSegment: 'knowledge' },
   table: { rootLabel: 'Tables', rootIcon: TableIcon, listSegment: 'tables' },
-  dashboard: { rootLabel: 'Dashboards', rootIcon: ChartColumn, listSegment: 'dashboards' },
 }
 
 /**