fix(tests): rewrite Robot for-loop as comprehension to preserve indentation

The Robot Framework `Catenate` keyword treats 2+ consecutive spaces as
field separators and strips them, which breaks Python's mandatory
indentation when a nested `assert` follows a `for` line. As a result
the "TUI Help Command Groups By Namespace" test produced a script with
a de-indented `assert` body, causing an IndentationError under
`python -c` and the test to fail with rc=1.

Rewrite the namespace-presence check as a single-line list
comprehension over the expected group headers, mirroring the pattern
already used by the sibling "Lists All Catalogued Commands" test in
the same file. The check is semantically equivalent — both fail with
the same diagnostic message when a group header is missing — but the
flattened form survives Robot's argument tokenisation intact.

ISSUES CLOSED: #3434

robot/tui_help_command.robot

@@ -34,8 +34,8 @@ TUI Help Command Groups By Namespace
     ...    state = MagicMock()
     ...    router = TuiCommandRouter(persona_registry=registry, persona_state=state)
     ...    result = router.handle("help", session_id="default")
-    ...    for group in ("Session:", "Persona:", "Plan:", "Utility:"):
-    ...        assert group in result, f"Missing group header {group!r} in output"
+    ...    missing = [g for g in ("Session:", "Persona:", "Plan:", "Utility:") if g not in result]
+    ...    assert not missing, f"Missing group headers: {missing}"
     ...    print("tui-help-groups-ok")
     ${result}=    Run Process    ${PYTHON}    -c    ${script}    shell=False    stderr=STDOUT
     Should Be Equal As Integers    ${result.rc}    0