revert: computer-use cua-driver (PR #16919) (#16927)

Reverts PR #16919 (commits dad10a78d, 413ee1a28, b4a8031b2, afb958829)
which was merged prematurely. Restoring the pre-merge state so #14817
and #15328 can be revisited as standing PRs.

Reverted commits:
- afb958829 fix(computer-use): harden image-rejection fallback + AUTHOR_MAP
- b4a8031b2 fix(computer-use): unwrap _multimodal tool results
- 413ee1a28 feat(computer-use): background focus-safe backend
- dad10a78d feat(computer-use): cua-driver backend, universal any-model schema

Co-authored-by: teknium1 <teknium@users.noreply.github.com>

website/docs/reference/toolsets-reference.md

@@ -61,7 +61,6 @@ Or in-session:
 | `feishu_drive` | `feishu_drive_add_comment`, `feishu_drive_list_comments`, `feishu_drive_list_comment_replies`, `feishu_drive_reply_comment` | Feishu/Lark drive comment operations. Scoped to the comment agent; not exposed on `hermes-cli` or other messaging toolsets. |
 | `file` | `patch`, `read_file`, `search_files`, `write_file` | File reading, writing, searching, and editing. |
 | `homeassistant` | `ha_call_service`, `ha_get_state`, `ha_list_entities`, `ha_list_services` | Smart home control via Home Assistant. Only available when `HASS_TOKEN` is set. |
-| `computer_use` | `computer_use` | Background macOS desktop control via cua-driver — does not steal cursor/focus. Works with any tool-capable model. macOS only; requires `cua-driver` on `$PATH`. |
 | `image_gen` | `image_generate` | Text-to-image generation via FAL.ai. |
 | `memory` | `memory` | Persistent cross-session memory management. |
 | `messaging` | `send_message` | Send messages to other platforms (Telegram, Discord, etc.) from within a session. |