fix(cli): prevent trailing space in picker-command completions

Commands that open pickers (/model, /skin, /personality) must not
receive a trailing space from the completion handler.  The TUI's
submit handler applies pending completions on Enter — adding a space
makes the input differ from the original, blocking picker execution.

Supersedes #15339.

hermes_cli/commands.py

@@ -865,6 +865,12 @@ class SlashCommandCompleter(Completer):
         except Exception:
             return {}
 
+    # Commands that open pickers when run without arguments.
+    # These should NOT receive a trailing space in completions because
+    # the TUI's submit handler applies completions on Enter if input differs,
+    # which blocks picker execution.
+    _PICKER_COMMANDS = frozenset({"model", "skin", "personality"})
+
     @staticmethod
     def _completion_text(cmd_name: str, word: str) -> str:
         """Return replacement text for a completion.
@@ -873,8 +879,16 @@ class SlashCommandCompleter(Completer):
         returning ``help`` would be a no-op and prompt_toolkit suppresses the
         menu. Appending a trailing space keeps the dropdown visible and makes
         backspacing retrigger it naturally.
+
+        However, commands that open pickers (model, skin, personality) should
+        NOT get a trailing space — the TUI would apply the completion on Enter
+        and block the picker from opening.
         """
-        return f"{cmd_name} " if cmd_name == word else cmd_name
+        if cmd_name != word:
+            return cmd_name
+        if cmd_name in SlashCommandCompleter._PICKER_COMMANDS:
+            return cmd_name
+        return f"{cmd_name} "
 
     @staticmethod
     def _extract_path_word(text: str) -> str | None:

tests/hermes_cli/test_commands.py

@@ -359,6 +359,23 @@ class TestSlashCommandCompleter:
 
         assert [item.text for item in completions] == ["help"]
 
+    # -- picker commands must NOT get trailing space ---------------------
+
+    def test_picker_commands_no_trailing_space(self):
+        """Picker commands (/model, /skin, /personality) must not get trailing space."""
+        for cmd in ("model", "skin", "personality"):
+            result = SlashCommandCompleter._completion_text(cmd, cmd)
+            assert result == cmd, f"/{cmd} should not have trailing space"
+
+    def test_non_picker_exact_match_gets_trailing_space(self):
+        """Regular commands like /help should still get trailing space on exact match."""
+        assert SlashCommandCompleter._completion_text("help", "help") == "help "
+
+    def test_partial_match_never_has_trailing_space_for_picker(self):
+        """Partial matches should never have trailing space regardless of command type."""
+        assert SlashCommandCompleter._completion_text("model", "mo") == "model"
+        assert SlashCommandCompleter._completion_text("help", "he") == "help"
+
     # -- non-slash input returns nothing ---------------------------------
 
     def test_no_completions_for_non_slash_input(self):