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.

tests/agent/test_prompt_builder.py

@@ -276,54 +276,6 @@ class TestBuildSkillsSystemPrompt:
         # "search" should appear only once per category
         assert result.count("- search") == 1
 
-    def test_compact_categories_demoted_to_names_only(self, monkeypatch, tmp_path):
-        """Posture-driven demotion keeps every skill NAME visible.
-
-        Demoted categories lose their descriptions, never their entries —
-        full pruning caused silent capability loss in a real workflow
-        (agent-created skills are the model's project memory, and models
-        don't rediscover them via skills_list once the index goes quiet).
-        """
-        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
-        for cat, name in (("social-media", "tweet-stuff"), ("github", "pr-review")):
-            d = tmp_path / "skills" / cat / name
-            d.mkdir(parents=True)
-            (d / "SKILL.md").write_text(
-                f"---\nname: {name}\ndescription: Does {name} things\n---\n"
-            )
-
-        result = build_skills_system_prompt(
-            compact_categories=frozenset({"social-media"})
-        )
-        # Coding-adjacent category keeps its full entry.
-        assert "pr-review" in result and "Does pr-review things" in result
-        # Demoted category: name stays visible, description is dropped.
-        assert "tweet-stuff" in result
-        assert "Does tweet-stuff things" not in result
-        assert "social-media [names only]" in result
-        # Disclosure note explains the demotion and how to load.
-        assert "skill_view" in result
-
-    def test_compact_categories_demote_nested_and_miss_cache_separately(
-        self, monkeypatch, tmp_path
-    ):
-        monkeypatch.setenv("HERMES_HOME", str(tmp_path))
-        d = tmp_path / "skills" / "social-media" / "twitter" / "thread-writer"
-        d.mkdir(parents=True)
-        (d / "SKILL.md").write_text(
-            "---\nname: thread-writer\ndescription: Write threads\n---\n"
-        )
-        # Nested category ("social-media/twitter") demoted via its parent:
-        # name visible, description gone.
-        compact = build_skills_system_prompt(
-            compact_categories=frozenset({"social-media"})
-        )
-        assert "thread-writer" in compact
-        assert "Write threads" not in compact
-        # Unfiltered call must not be served from the compacted cache entry.
-        full = build_skills_system_prompt()
-        assert "Write threads" in full
-
     def test_excludes_incompatible_platform_skills(self, monkeypatch, tmp_path):
         """Skills with platforms: [macos] should not appear on Linux."""
         monkeypatch.setenv("HERMES_HOME", str(tmp_path))