fix(integrations): raise actionable error on malformed EXTRA_ARGS quoting

Wrap `shlex.split` in `_apply_extra_args_env_var` so an unmatched quote
in `SPECIFY_INTEGRATION_<KEY>_EXTRA_ARGS` surfaces a clear `ValueError`
naming the offending env var and showing the invalid value, instead of
crashing workflow dispatch with a bare shlex traceback. Adds a new test
locking the actionable error path.

Addresses Copilot review feedback on #2596.

Author: doquanghuy

src/specify_cli/integrations/base.py

@@ -164,8 +164,18 @@ def _apply_extra_args_env_var(self, args: list[str]) -> None:
             f"SPECIFY_INTEGRATION_{self.key.upper().replace('-', '_')}_EXTRA_ARGS"
         )
         extra = os.environ.get(env_name, "").strip()
-        if extra:
-            args.extend(shlex.split(extra))
+        if not extra:
+            return
+        try:
+            tokens = shlex.split(extra)
+        except ValueError as exc:
+            raise ValueError(
+                f"{env_name} is not parseable as a POSIX-quoted command line "
+                f"(value: {extra!r}). shlex reported: {exc}. "
+                f"Use single or double quotes to group multi-word values, e.g. "
+                f'{env_name}=\'--flag "value with spaces"\'.'
+            ) from exc
+        args.extend(tokens)
 
     def build_command_invocation(self, command_name: str, args: str = "") -> str:
         """Build the native slash-command invocation for a Spec Kit command.

tests/integrations/test_extra_args.py

@@ -135,6 +135,21 @@ def test_env_var_multi_token_parsed_via_shlex(monkeypatch):
     ]
 
 
+def test_malformed_quoting_raises_actionable_value_error(monkeypatch):
+    """An unmatched quote in the env-var value must surface a clear
+    error naming the offending env var and showing the invalid value,
+    rather than crashing workflow dispatch with a bare shlex traceback."""
+    monkeypatch.setenv(
+        "SPECIFY_INTEGRATION_CLAUDE_EXTRA_ARGS",
+        '--flag "unterminated',
+    )
+    with pytest.raises(ValueError) as excinfo:
+        _ClaudeStub().build_exec_args("p")
+    msg = str(excinfo.value)
+    assert "SPECIFY_INTEGRATION_CLAUDE_EXTRA_ARGS" in msg
+    assert "--flag \"unterminated" in msg
+
+
 def test_env_var_empty_or_whitespace_is_noop(monkeypatch):
     """An env var set to '' or '   ' is treated as unset."""
     monkeypatch.setenv("SPECIFY_INTEGRATION_CLAUDE_EXTRA_ARGS", "   ")