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>

tools/computer_use/__init__.py

@@ -1,43 +0,0 @@
-"""Computer use toolset — universal (any-model) macOS desktop control.
-
-Architecture
-------------
-This toolset drives macOS apps through cua-driver's background computer-use
-primitive (SkyLight private SPIs for focus-without-raise + pid-scoped event
-posting). Unlike #4562's pyautogui backend, it does NOT steal the user's
-cursor, keyboard focus, or Space — the agent and the user can co-work on the
-same machine.
-
-Unlike #4562's Anthropic-native `computer_20251124` tool, the schema here is
-a plain OpenAI function-calling schema that every tool-capable model can
-drive. Vision models get SOM (set-of-mark) captures — a screenshot with
-numbered overlays on every interactable element plus the AX tree — so they
-click by element index instead of pixel coordinates. Non-vision models can
-drive via the AX tree alone.
-
-Wiring
-------
-* `tool.py`       — registers the `computer_use` tool via tools.registry.
-* `backend.py`    — abstract `ComputerUseBackend`; swappable implementation.
-* `cua_backend.py`— default backend; speaks MCP over stdio to `cua-driver`.
-* `schema.py`     — shared schema + docstring for the generic `computer_use`
-                    tool. Model-agnostic.
-* `capture.py`    — screenshot post-processing (PNG coercion, sizing, SOM
-                    overlay if the backend did not).
-
-The outer integration points (multimodal tool-result plumbing, screenshot
-eviction in the Anthropic adapter, image-aware token estimation, the
-COMPUTER_USE_GUIDANCE prompt block, approval hook, and the skill) live
-alongside this package. See agent/anthropic_adapter.py and
-agent/prompt_builder.py for the salvaged hunks from PR #4562.
-"""
-
-from __future__ import annotations
-
-# Re-export the public surface so `from tools.computer_use import ...` works.
-from tools.computer_use.tool import (  # noqa: F401
-    handle_computer_use,
-    set_approval_callback,
-    check_computer_use_requirements,
-    get_computer_use_schema,
-)