feat(hermes): Hermes Agent harness support, rebased to a Hermes-only diff

Rebase of PR #1922 onto current dev: the ~14 files of v6.1.0-era
codex/release drift are dropped, the porting-guide edits (stale against
the post-prune rewrite, no Hermes content) are dropped, and the Hermes
surface is kept intact: .hermes-plugin/ (on_session_start bootstrap
injection), tests/hermes/ (20 tests, passing), docs/README.hermes.md,
references/hermes-tools.md, the Platform Adaptation row, README section,
and Python ignores.

Known open items from review, unchanged by this rebase: the injection
mechanism uses ctx.inject_message from on_session_start, which the
official plugin guide does not document (pre_llm_call returning
{"context": ...} is the sanctioned path), skills are not registered via
ctx.register_skill, and the acceptance transcript predates the fix.

Co-authored-by: kumarabd <kumarabd@users.noreply.github.com>

tests/hermes/test_plugin.py

@@ -0,0 +1,105 @@
+import os
+import sys
+import importlib
+import pytest
+
+# Point at the plugin directory
+_PLUGIN_DIR = os.path.join(os.path.dirname(__file__), "../../.hermes-plugin")
+sys.path.insert(0, os.path.abspath(_PLUGIN_DIR))
+
+BOOTSTRAP_MARKER = "superpowers:using-superpowers bootstrap for hermes"
+
+
+def _load_plugin():
+    """Re-import plugin module fresh (clears module-level cache)."""
+    if "__init__" in sys.modules:
+        del sys.modules["__init__"]
+    return importlib.import_module("__init__")
+
+
+class TestPluginRegistration:
+    def test_register_attaches_session_start_hook(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        mock_ctx.register_hook.assert_called_once()
+        event_name = mock_ctx.register_hook.call_args[0][0]
+        assert event_name == "on_session_start"
+
+
+class TestBootstrapInjection:
+    def test_first_session_start_injects_bootstrap(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        assert len(mock_ctx._injected) == 1
+        assert BOOTSTRAP_MARKER in mock_ctx._injected[0]["content"]
+
+    def test_injection_uses_user_role(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        assert mock_ctx._injected[0]["role"] == "user"
+
+    def test_dedup_skips_on_same_session_id(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        handler(session_id="sess-1", model="test-model", platform="test")
+        assert len(mock_ctx._injected) == 1
+
+    def test_reinjects_on_new_session_id(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        handler(session_id="sess-2", model="test-model", platform="test")
+        assert len(mock_ctx._injected) == 2
+
+    def test_missing_skill_file_skips_silently(self, mock_ctx, tmp_path):
+        plugin = _load_plugin()
+        plugin._bootstrap_cache = None
+        plugin._SKILLS_DIR = str(tmp_path / "nonexistent")
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        assert len(mock_ctx._injected) == 0
+
+    def test_cache_populated_after_first_call(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin._bootstrap_cache = None
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        assert plugin._bootstrap_cache is not None
+        assert plugin._bootstrap_cache is not False
+
+
+class TestBootstrapContent:
+    def test_contains_extremely_important_tags(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        content = mock_ctx._injected[0]["content"]
+        assert "<EXTREMELY_IMPORTANT>" in content
+        assert "</EXTREMELY_IMPORTANT>" in content
+
+    def test_frontmatter_stripped(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        content = mock_ctx._injected[0]["content"]
+        assert "---\nname:" not in content
+
+    def test_tool_mapping_present(self, mock_ctx):
+        plugin = _load_plugin()
+        plugin.register(mock_ctx)
+        handler = mock_ctx._hooks["on_session_start"]
+        handler(session_id="sess-1", model="test-model", platform="test")
+        content = mock_ctx._injected[0]["content"]
+        assert "Hermes tool mapping" in content
+        assert "read_file" in content