feat(computer-use): cua-driver backend, universal any-model schema

Background macOS desktop control via cua-driver MCP — does NOT steal the
user's cursor or keyboard focus, works with any tool-capable model.

Replaces the Anthropic-native `computer_20251124` approach from the
abandoned #4562 with a generic OpenAI function-calling schema plus SOM
(set-of-mark) captures so Claude, GPT, Gemini, and open models can all
drive the desktop via numbered element indices.

- `tools/computer_use/` package — swappable ComputerUseBackend ABC +
  CuaDriverBackend (stdio MCP client to trycua/cua's cua-driver binary).
- Universal `computer_use` tool with one schema for all providers.
  Actions: capture (som/vision/ax), click, double_click, right_click,
  middle_click, drag, scroll, type, key, wait, list_apps, focus_app.
- Multimodal tool-result envelope (`_multimodal=True`, OpenAI-style
  `content: [text, image_url]` parts) that flows through
  handle_function_call into the tool message. Anthropic adapter converts
  into native `tool_result` image blocks; OpenAI-compatible providers
  get the parts list directly.
- Image eviction in convert_messages_to_anthropic: only the 3 most
  recent screenshots carry real image data; older ones become text
  placeholders to cap per-turn token cost.
- Context compressor image pruning: old multimodal tool results have
  their image parts stripped instead of being skipped.
- Image-aware token estimation: each image counts as a flat 1500 tokens
  instead of its base64 char length (~1MB would have registered as
  ~250K tokens before).
- COMPUTER_USE_GUIDANCE system-prompt block — injected when the toolset
  is active.
- Session DB persistence strips base64 from multimodal tool messages.
- Trajectory saver normalises multimodal messages to text-only.
- `hermes tools` post-setup installs cua-driver via the upstream script
  and prints permission-grant instructions.
- CLI approval callback wired so destructive computer_use actions go
  through the same prompt_toolkit approval dialog as terminal commands.
- Hard safety guards at the tool level: blocked type patterns
  (curl|bash, sudo rm -rf, fork bomb), blocked key combos (empty trash,
  force delete, lock screen, log out).
- Skill `apple/macos-computer-use/SKILL.md` — universal (model-agnostic)
  workflow guide.
- Docs: `user-guide/features/computer-use.md` plus reference catalog
  entries.

44 new tests in tests/tools/test_computer_use.py covering schema
shape (universal, not Anthropic-native), dispatch routing, safety
guards, multimodal envelope, Anthropic adapter conversion, screenshot
eviction, context compressor pruning, image-aware token estimation,
run_agent helpers, and universality guarantees.

469/469 pass across tests/tools/test_computer_use.py + the affected
agent/ test suites.

- `model_tools.py` provider-gating: the tool is available to every
  provider. Providers without multi-part tool message support will see
  text-only tool results (graceful degradation via `text_summary`).
- Anthropic server-side `clear_tool_uses_20250919` — deferred;
  client-side eviction + compressor pruning cover the same cost ceiling
  without a beta header.

- macOS only. cua-driver uses private SkyLight SPIs
  (SLEventPostToPid, SLPSPostEventRecordTo,
  _AXObserverAddNotificationAndCheckRemote) that can break on any macOS
  update. Pin with HERMES_CUA_DRIVER_VERSION.
- Requires Accessibility + Screen Recording permissions — the post-setup
  prints the Settings path.

Supersedes PR #4562 (pyautogui/Quartz foreground backend, Anthropic-
native schema). Credit @0xbyt4 for the original #3816 groundwork whose
context/eviction/token design is preserved here in generic form.

cli.py

@@ -9208,6 +9208,27 @@ class HermesCLI:
             choices.append("view")
         return choices
 
+    def _computer_use_approval_callback(self, action: str, args: dict, summary: str) -> str:
+        """Adapt the generic approval UI for the computer_use tool.
+
+        The computer_use handler expects verdicts of the form
+        `approve_once` | `approve_session` | `always_approve` | `deny`.
+        The CLI's built-in approval UI returns `once` | `session` | `always`
+        | `deny`. Translate between the two.
+        """
+        # Build a command-ish string so the existing UI renders something
+        # meaningful. `summary` is already a one-line human description.
+        verdict = self._approval_callback(
+            command=f"computer_use: {summary}",
+            description=f"Allow computer_use to perform `{action}`?",
+        )
+        return {
+            "once": "approve_once",
+            "session": "approve_session",
+            "always": "always_approve",
+            "deny": "deny",
+        }.get(verdict, "deny")
+
     def _handle_approval_selection(self) -> None:
         """Process the currently selected dangerous-command approval choice."""
         state = self._approval_state
@@ -10444,6 +10465,16 @@ class HermesCLI:
         set_approval_callback(self._approval_callback)
         set_secret_capture_callback(self._secret_capture_callback)
 
+        # Computer-use shares the same approval UI (prompt_toolkit dialog).
+        # The tool handler expects a 3-arg callback (action, args, summary)
+        # and returns "approve_once" | "approve_session" | "always_approve"
+        # | "deny". Adapt our existing generic callback.
+        try:
+            from tools.computer_use_tool import set_approval_callback as _set_cu_cb
+            _set_cu_cb(self._computer_use_approval_callback)
+        except ImportError:
+            pass  # computer_use extras not installed
+
         # Ensure tirith security scanner is available (downloads if needed).
         # Warn the user if tirith is enabled in config but not available,
         # so they know command security scanning is degraded.