chore: remove dead code — 28 unused functions/classes across 16 files

Vulture + per-symbol verification (whole-repo grep incl. tests, string
literals, getattr, decorator/registry/argparse dispatch) confirmed each of
these has zero callers anywhere — not reachable via any dynamic-dispatch path,
not referenced by tests, not re-exported.

Removed:
- acp_adapter/tools.py: _build_patch_mode_content
- agent/anthropic_adapter.py: read_claude_managed_key (diagnostics-only, never called)
- agent/bedrock_adapter.py: get_bedrock_model_ids
- agent/browser_registry.py: get_active_browser_provider
- agent/chat_completion_helpers.py: _take_request_client (x2 nested closures, never invoked)
- gateway/platforms/weixin.py: _rewrite_headers_for_weixin, _rewrite_table_block_for_weixin
- hermes_cli/banner.py: _skin_branding
- hermes_cli/debug.py: _delete_hint
- hermes_cli/gateway.py: _setup_email, _setup_sms, _setup_yuanbao
  (platform keys absent from the _builtin_setup_fn dispatch dict; handled by
  the _setup_standard_platform fallback)
- hermes_cli/kanban_db.py: set_max_runtime, active_run
- hermes_cli/kanban_diagnostics.py: severity_of_highest, _latest_clean_event_ts
- hermes_cli/main.py: _build_provider_choices, cmd_portal
  (portal subcommand is wired via portal_cli.add_parser, not this wrapper)
- hermes_cli/model_switch.py: CustomAutoResult (orphaned by the switch_model() extraction)
- hermes_cli/models.py: format_model_pricing_table, fetch_nous_account_tier
- hermes_cli/portal_cli.py: _nous_portal_base_url
- hermes_cli/proxy/server.py: handle_models_fallback (defined but never registered on the router)
- tools/computer_use/cua_backend.py: _parse_element, _is_arm_mac
- tools/file_operations.py: _get_safe_write_root (prod uses the imported
  agent.file_safety.get_safe_write_root directly)
- tools/skills_tool.py: _load_category_description

Also dropped two imports left unused by the removals:
- tools/file_operations.py: get_safe_write_root alias
- tools/computer_use/cua_backend.py: import platform

Pure deletion: -551 LOC. No behavior change. Test files covering the edited
modules pass (640/640); the broader suite's pre-existing/env-dependent
failures reproduce unchanged on origin/main.

tools/computer_use/cua_backend.py

@@ -22,7 +22,6 @@ import base64
 import json
 import logging
 import os
-import platform
 import re
 import shutil
 import sys
@@ -77,12 +76,6 @@ _ELEMENT_LINE_RE = re.compile(
 
 def _is_macos() -> bool:
     return sys.platform == "darwin"
-
-
-def _is_arm_mac() -> bool:
-    return _is_macos() and platform.machine() == "arm64"
-
-
 def cua_driver_binary_available() -> bool:
     """True if `cua-driver` is on $PATH or HERMES_CUA_DRIVER_CMD resolves."""
     return bool(shutil.which(_CUA_DRIVER_CMD))
@@ -705,29 +698,3 @@ class CuaDriverBackend(ComputerUseBackend):
             message = data
         return ActionResult(ok=ok, action=name, message=message,
                             meta=data if isinstance(data, dict) else {})
-
-
-def _parse_element(d: Dict[str, Any]) -> UIElement:
-    bounds = d.get("bounds") or (0, 0, 0, 0)
-    if isinstance(bounds, dict):
-        bounds = (
-            int(bounds.get("x", 0)),
-            int(bounds.get("y", 0)),
-            int(bounds.get("w", bounds.get("width", 0))),
-            int(bounds.get("h", bounds.get("height", 0))),
-        )
-    elif isinstance(bounds, (list, tuple)) and len(bounds) == 4:
-        bounds = tuple(int(v) for v in bounds)
-    else:
-        bounds = (0, 0, 0, 0)
-    return UIElement(
-        index=int(d.get("index", 0)),
-        role=str(d.get("role", "") or ""),
-        label=str(d.get("label", "") or ""),
-        bounds=bounds,  # type: ignore[arg-type]
-        app=str(d.get("app", "") or ""),
-        pid=int(d.get("pid", 0) or 0),
-        window_id=int(d.get("windowId", 0) or 0),
-        attributes={k: v for k, v in d.items()
-                    if k not in {"index", "role", "label", "bounds", "app", "pid", "windowId"}},
-    )