feat: secure skill env setup on load (core #688)

When a skill declares required_environment_variables in its YAML
frontmatter, missing env vars trigger a secure TUI prompt (identical
to the sudo password widget) when the skill is loaded. Secrets flow
directly to ~/.hermes/.env, never entering LLM context.

Key changes:
- New required_environment_variables frontmatter field for skills
- Secure TUI widget (masked input, 120s timeout)
- Gateway safety: messaging platforms show local setup guidance
- Legacy prerequisites.env_vars normalized into new format
- Remote backend handling: conservative setup_needed=True
- Env var name validation, file permissions hardened to 0o600
- Redact patterns extended for secret-related JSON fields
- 12 existing skills updated with prerequisites declarations
- ~48 new tests covering skip, timeout, gateway, remote backends
- Dynamic panel widget sizing (fixes hardcoded width from original PR)

Cherry-picked from PR #723 by kshitijk4poor, rebased onto current main
with conflict resolution.

Fixes #688

Co-authored-by: kshitijk4poor <kshitijk4poor@users.noreply.github.com>

tests/test_cli_secret_capture.py

@@ -0,0 +1,147 @@
+import queue
+import threading
+import time
+from unittest.mock import patch
+
+import cli as cli_module
+import tools.skills_tool as skills_tool_module
+from cli import HermesCLI
+from hermes_cli.callbacks import prompt_for_secret
+from tools.skills_tool import set_secret_capture_callback
+
+
+class _FakeBuffer:
+    def __init__(self):
+        self.reset_called = False
+
+    def reset(self):
+        self.reset_called = True
+
+
+class _FakeApp:
+    def __init__(self):
+        self.invalidated = False
+        self.current_buffer = _FakeBuffer()
+
+    def invalidate(self):
+        self.invalidated = True
+
+
+def _make_cli_stub(with_app=False):
+    cli = HermesCLI.__new__(HermesCLI)
+    cli._app = _FakeApp() if with_app else None
+    cli._last_invalidate = 0.0
+    cli._secret_state = None
+    cli._secret_deadline = 0
+    return cli
+
+
+def test_secret_capture_callback_can_be_completed_from_cli_state_machine():
+    cli = _make_cli_stub(with_app=True)
+    results = []
+
+    with patch("hermes_cli.callbacks.save_env_value_secure") as save_secret:
+        save_secret.return_value = {
+            "success": True,
+            "stored_as": "TENOR_API_KEY",
+            "validated": False,
+        }
+
+        thread = threading.Thread(
+            target=lambda: results.append(
+                cli._secret_capture_callback("TENOR_API_KEY", "Tenor API key")
+            )
+        )
+        thread.start()
+
+        deadline = time.time() + 2
+        while cli._secret_state is None and time.time() < deadline:
+            time.sleep(0.01)
+
+        assert cli._secret_state is not None
+        cli._submit_secret_response("super-secret-value")
+        thread.join(timeout=2)
+
+    assert results[0]["success"] is True
+    assert results[0]["stored_as"] == "TENOR_API_KEY"
+    assert results[0]["skipped"] is False
+
+
+def test_cancel_secret_capture_marks_setup_skipped():
+    cli = _make_cli_stub()
+    cli._secret_state = {
+        "response_queue": queue.Queue(),
+        "var_name": "TENOR_API_KEY",
+        "prompt": "Tenor API key",
+        "metadata": {},
+    }
+    cli._secret_deadline = 123
+
+    cli._cancel_secret_capture()
+
+    assert cli._secret_state is None
+    assert cli._secret_deadline == 0
+
+
+def test_secret_capture_uses_getpass_without_tui():
+    cli = _make_cli_stub()
+
+    with patch("hermes_cli.callbacks.getpass.getpass", return_value="secret-value"), patch(
+        "hermes_cli.callbacks.save_env_value_secure"
+    ) as save_secret:
+        save_secret.return_value = {
+            "success": True,
+            "stored_as": "TENOR_API_KEY",
+            "validated": False,
+        }
+        result = prompt_for_secret(cli, "TENOR_API_KEY", "Tenor API key")
+
+    assert result["success"] is True
+    assert result["stored_as"] == "TENOR_API_KEY"
+    assert result["skipped"] is False
+
+
+def test_secret_capture_timeout_clears_hidden_input_buffer():
+    cli = _make_cli_stub(with_app=True)
+    cleared = {"value": False}
+
+    def clear_buffer():
+        cleared["value"] = True
+
+    cli._clear_secret_input_buffer = clear_buffer
+
+    with patch("hermes_cli.callbacks.queue.Queue.get", side_effect=queue.Empty), patch(
+        "hermes_cli.callbacks._time.monotonic",
+        side_effect=[0, 121],
+    ):
+        result = prompt_for_secret(cli, "TENOR_API_KEY", "Tenor API key")
+
+    assert result["success"] is True
+    assert result["skipped"] is True
+    assert result["reason"] == "timeout"
+    assert cleared["value"] is True
+
+
+def test_cli_chat_registers_secret_capture_callback():
+    clean_config = {
+        "model": {
+            "default": "anthropic/claude-opus-4.6",
+            "base_url": "https://openrouter.ai/api/v1",
+            "provider": "auto",
+        },
+        "display": {"compact": False, "tool_progress": "all"},
+        "agent": {},
+        "terminal": {"env_type": "local"},
+    }
+
+    with patch("cli.get_tool_definitions", return_value=[]), patch.dict(
+        "os.environ", {"LLM_MODEL": "", "HERMES_MAX_ITERATIONS": ""}, clear=False
+    ), patch.dict(cli_module.__dict__, {"CLI_CONFIG": clean_config}):
+        cli_obj = HermesCLI()
+        with patch.object(cli_obj, "_ensure_runtime_credentials", return_value=False):
+            cli_obj.chat("hello")
+
+    try:
+        assert skills_tool_module._secret_capture_callback == cli_obj._secret_capture_callback
+    finally:
+        set_secret_capture_callback(None)