fix: spawn_test never raises — coerce env/command to str, wrap unexpected errors (#34)

Closes #34

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bcc_core.py

@@ -1591,12 +1591,29 @@ def spawn_test(data: dict, timeout: float = 3.0) -> dict:
                 "crashed"        — exited with a non-zero code before timeout
                 "not_found"      — command could not be resolved to an executable
                 "not_applicable" — remote server or no command; nothing to spawn
+                "error"          — unexpected internal failure while spawning/observing
       returncode: int | None
       stderr:    str  (first ~4 KB)
       detail:    str
 
+    Never raises: the GUI threads (Test launch / Test all) re-enable their
+    buttons only when a result arrives, so an escaping exception would leave
+    the UI stuck. Anything unexpected comes back as outcome "error".
+
     Run this off the UI thread — it blocks for up to `timeout` seconds.
     """
+    try:
+        return _spawn_test_impl(data, timeout)
+    except Exception as e:
+        return {
+            "outcome": "error",
+            "returncode": None,
+            "stderr": "",
+            "detail": f"unexpected error: {e!r}",
+        }
+
+
+def _spawn_test_impl(data: dict, timeout: float) -> dict:
     if "url" in data and "command" not in data:
         return {
             "outcome": "not_applicable",
@@ -1605,7 +1622,9 @@ def spawn_test(data: dict, timeout: float = 3.0) -> dict:
             "detail": "remote server",
         }
 
-    cmd = (data.get("command") or "").strip()
+    # str() first: pasted JSON can legally carry a non-string here and the
+    # value never round-trips through the editor before a Test all run.
+    cmd = str(data.get("command") or "").strip()
     if not cmd:
         return {
             "outcome": "not_applicable",
@@ -1627,7 +1646,8 @@ def spawn_test(data: dict, timeout: float = 3.0) -> dict:
     args_list = [resolved_cmd] + [str(a) for a in (data.get("args") or [])]
 
     merged_env = {**os.environ, "PATH": augmented_path()}
-    merged_env.update(data.get("env") or {})
+    # Popen rejects non-string env values; pasted JSON may carry numbers.
+    merged_env.update({str(k): str(v) for k, v in (data.get("env") or {}).items()})
 
     stderr_chunks: list[bytes] = []