fix(computer_use): reconcile Linux gate with stale "gated off" comments

The runtime gate (check_computer_use_requirements) and the hermes tools
platform_gate both enable linux alongside darwin/win32, but several
docstrings/comments still described Linux as "alpha, gated off until it
flips upstream" — contradicting the code that ships it. Bring the prose in
line with the gate that's actually live:

- tool.py / cua_backend.py module docstrings: Linux is enabled (X11 today,
  Wayland via XWayland), not gated off.
- toolsets.py description and hermes tools display name: (macOS/Windows) ->
  (macOS/Windows/Linux).

No behavior change — the gate already allowed all three platforms.

hermes_cli/tools_config.py

@@ -516,9 +516,10 @@ TOOL_CATEGORIES = {
         ],
     },
     "computer_use": {
-        "name": "Computer Use (macOS/Windows)",
+        "name": "Computer Use (macOS/Windows/Linux)",
         "icon": "🖱️",
-        # Runtime backends ship for macOS + Windows today; Linux is alpha.
+        # Runtime backends ship for macOS, Windows, and Linux (X11 today,
+        # Wayland via XWayland). Per-host gaps surface via `computer-use doctor`.
         "platform_gate": ["darwin", "win32", "linux"],
         "providers": [
             {

tools/computer_use/cua_backend.py

@@ -1,4 +1,4 @@
-"""Cua-driver backend (macOS + Windows).
+"""Cua-driver backend (macOS, Windows, Linux).
 
 Speaks MCP over stdio to `cua-driver`. The Python `mcp` SDK is async, so we
 run a dedicated asyncio event loop on a background thread and marshal sync
@@ -6,14 +6,16 @@ calls through it.
 
 The same `cua-driver call <tool>` surface (click, type_text, hotkey, drag,
 scroll, screenshot, launch_app, list_apps, list_windows, get_window_state,
-move_cursor, wait) works identically across macOS + Windows — cua-driver's
-PARITY matrix marks every action tool VERIFIED on Windows in the
-cross-platform Rust port (`cua-driver-rs`).
+move_cursor, wait) works identically across macOS, Windows, and Linux —
+cua-driver's PARITY matrix marks the action tools VERIFIED on macOS and
+Windows in the cross-platform Rust port (`cua-driver-rs`).
 
-Linux support exists in cua-driver-rs but is alpha today — Linux PARITY
-rows are mostly OPEN, not VERIFIED — so it's gated off in
-`check_computer_use_requirements` until that flips upstream. The plumbing
-in this file is OS-agnostic, so flipping that gate later is one-line.
+Linux is the most recent runtime (X11 today, Wayland via XWayland; pure-
+Wayland progress tracked upstream). It is enabled in
+`check_computer_use_requirements` alongside macOS and Windows. The plumbing
+in this file is OS-agnostic; per-host gaps (no DISPLAY, missing AT-SPI,
+etc.) surface as specific blocked checks via `hermes computer-use doctor`
+rather than failing silently.
 
 Install:
   - **macOS**:

tools/computer_use/tool.py

@@ -1,12 +1,15 @@
 """Entry point for the `computer_use` tool.
 
-Universal (any-model) desktop control across macOS + Windows via
+Universal (any-model) desktop control across macOS, Windows, and Linux via
 cua-driver's background computer-use primitive. Replaces #4562's
 Anthropic-native `computer_20251124` approach — the schema here is standard
 OpenAI function-calling so every tool-capable model can drive it.
 
-Linux support exists in cua-driver-rs (alpha — PARITY rows are mostly
-OPEN today, not VERIFIED) and is gated off here until it flips upstream.
+Linux is the most recent runtime (X11 + Wayland, via cua-driver-rs's
+AT-SPI tree path); it is enabled here alongside macOS and Windows. When a
+host's display server or accessibility stack isn't reachable, cua-driver's
+`health_report` (surfaced by `hermes computer-use doctor`) reports the
+exact blocked check rather than the toolset silently failing.
 
 Return contract
 ---------------

toolsets.py

@@ -142,7 +142,7 @@ TOOLSETS = {
 
     "computer_use": {
         "description": (
-            "Background desktop control via cua-driver (macOS/Windows) — "
+            "Background desktop control via cua-driver (macOS/Windows/Linux) — "
             "screenshots, mouse, keyboard, scroll, drag. Does NOT steal the "
             "user's cursor or keyboard focus. Works with any tool-capable model."
         ),