fix: parse malformed schedule_days string from Robot Framework

Robot Framework's Create Dictionary converts ['mon', 'tue'] into a
string. Add _parse_schedule_days to handle JSON/Python-literal parsing
before Pydantic type validation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/server/models/config.py

@@ -2,7 +2,7 @@ import ast
 import json
 from typing import Any, Dict, List, Optional
 
-from pydantic import BaseModel, Field, ValidationError, field_validator
+from pydantic import BaseModel, Field, ValidationError, field_validator, model_validator
 
 _VALID_DAYS = frozenset(["mon", "tue", "wed", "thu", "fri", "sat", "sun"])
 _ALL_DAYS = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]
@@ -74,6 +74,40 @@ class SchedulerConfig(BaseModel):
             )
         return v
 
+    @classmethod
+    def _parse_schedule_days(cls, v):
+        """Parse schedule_days that may arrive as a malformed string.
+
+        Robot Framework's Create Dictionary converts Python-style lists
+        like ['monday', 'tuesday'] into strings. Handle that here before
+        Pydantic's type validation runs.
+        """
+        if not isinstance(v, str):
+            return v
+        # Try JSON first (double-quoted), then Python literal (single-quoted)
+        for parse_fn in (json.loads, ast.literal_eval):
+            try:
+                parsed = parse_fn(v)
+                if isinstance(parsed, list):
+                    return parsed
+            except Exception:
+                pass
+        # Cannot parse - let Pydantic handle the error
+        return v
+
+    @model_validator(mode="before")
+    @classmethod
+    def _pre_validate(cls, data):
+        """Handle malformed schedule_days from Robot Framework before type validation."""
+        if isinstance(data, dict):
+            sd = data.get("schedule_days")
+            if isinstance(sd, str):
+                parsed = cls._parse_schedule_days(sd)
+                if isinstance(parsed, list):
+                    data = dict(data)
+                    data["schedule_days"] = parsed
+        return data
+
     @field_validator("schedule_days")
     @classmethod
     def validate_schedule_days(cls, v: List[str]) -> List[str]: