feat: add recursive namespace routing and standalone runner polish

- introduce namespace-aware routing with RootParseResult, RouteResult, and InvocationContext
- register submenus as FalyxNamespace entries and resolve them through _entry_map
- refactor FalyxParser to parse only root options and leave recursive routing to Falyx
- add prepare_route, resolve_route, and route dispatch flow to Falyx
- update validator and completer to understand namespace entries and route results
- unify help/TLDR rendering APIs and add custom_tldr support on Command
- tighten Command.resolve_args error handling and parser type validation
- improve CommandRunner dependency validation and argv handling
- add BottomBar.has_items and improve wrapped executor error messages
- add tests for execution options, resolve_args, command runner, and route-aware validation

tests/test_execution_option.py

@@ -0,0 +1,30 @@
+import pytest
+
+from falyx.execution_option import ExecutionOption
+
+
+def test_execution_option_accepts_valid_string_values():
+    assert ExecutionOption("summary") == ExecutionOption.SUMMARY
+    assert ExecutionOption("retry") == ExecutionOption.RETRY
+    assert ExecutionOption("confirm") == ExecutionOption.CONFIRM
+
+
+def test_execution_option_rejects_invalid_string():
+    with pytest.raises(ValueError, match="Invalid ExecutionOption: 'invalid'"):
+        ExecutionOption("invalid")
+
+
+def test_execution_option_normalizes_case_and_whitespace():
+    assert ExecutionOption("  SUMMARY  ") == ExecutionOption.SUMMARY
+    assert ExecutionOption("ReTrY") == ExecutionOption.RETRY
+    assert ExecutionOption("\tconfirm\n") == ExecutionOption.CONFIRM
+
+
+def test_execution_option_rejects_non_string():
+    with pytest.raises(ValueError, match="Invalid ExecutionOption: 123"):
+        ExecutionOption(123)
+
+
+def test_execution_option_error_lists_valid_values():
+    with pytest.raises(ValueError, match="Must be one of: summary, retry, confirm"):
+        ExecutionOption("invalid")