opentui(phase3): launcher integration — HERMES_TUI_ENGINE dual-engine

hermes --tui launches the native OpenTUI engine (Bun) when
HERMES_TUI_ENGINE=opentui (env) or display.tui_engine=opentui (config);
Ink stays the default and the shipping path is untouched.

- _resolve_tui_engine() (env > config > ink); refuses opentui on
  Windows/Termux (no Bun) -> falls back to ink with a notice.
- _make_opentui_argv() -> [bun, src/entry.real.tsx] (no build step).
- _bun_bin() with HERMES_BUN override.
- Branch at top of _make_tui_argv BEFORE _ensure_tui_node (Bun-only host
  must not bootstrap Node).
- Gate _launch_tui NODE_OPTIONS/--max-old-space-size on engine==ink (Bun
  is JSC; the V8 flag errors/ignores).

Verified end-to-end via tmux: real hermes --tui -> Bun -> OpenTUI ->
real Python gateway streamed a real reply. No-flag default still ink.

hermes_cli/tools_config.py

@@ -1437,10 +1437,6 @@ def _get_platform_tools(
             continue
         if ts_def.get("includes"):
             continue
-        # Posture toolsets (e.g. ``coding``) are session-level selections made
-        # by agent/coding_context.py — not per-platform capabilities to recover.
-        if ts_def.get("posture"):
-            continue
         ts_tools = set(resolve_toolset(ts_key))
         if not ts_tools or not ts_tools.issubset(platform_tool_universe):
             continue
@@ -2182,13 +2178,8 @@ def _toolset_needs_configuration_prompt(
         tts_cfg = config.get("tts", {})
         return not isinstance(tts_cfg, dict) or "provider" not in tts_cfg
     if ts_key == "web":
-        # Web works out of the box via Parallel's free Search MCP (no key), so
-        # don't force setup just because ``web.backend`` is unset — only prompt
-        # when web isn't actually usable (e.g. an explicit backend configured
-        # without its credentials). Lazy import: web_tools is heavy and most
-        # tools_config callers don't need it.
-        from tools.web_tools import check_web_api_key
-        return not check_web_api_key()
+        web_cfg = config.get("web", {})
+        return not isinstance(web_cfg, dict) or "backend" not in web_cfg
     if ts_key == "browser":
         browser_cfg = config.get("browser", {})
         return not isinstance(browser_cfg, dict) or "cloud_provider" not in browser_cfg