Fix sync_schedule validation to accept multi-time daily format

The scheduler.py already supported "daily HH:MM,HH:MM,HH:MM" format
(commit 5f27d05), but config.py validation regex only accepted single
time "daily HH:MM", causing data-refresh to crash on startup.

Also adds:
- tests/test_config_sync_schedule.py (16 test cases)
- Makefile with validate-config target for CI/CD integration

Makefile

@@ -0,0 +1,75 @@
+# AI Data Analyst - Development Makefile
+#
+# Usage:
+#   make              - show help
+#   make test         - run all tests
+#   make test-config  - run config-related tests only
+#   make validate-config CONFIG_DIR=path/to/config  - validate data_description.md
+#   make lint         - placeholder for future linting
+
+SHELL   := /bin/bash
+PYTHON  := .venv/bin/python
+PYTEST  := .venv/bin/pytest
+
+# Optional: path to config directory containing data_description.md
+# Default: config/ (relative to project root)
+CONFIG_DIR ?= config
+
+.PHONY: help test test-config validate-config lint
+
+# Default target
+help:
+	@echo "Available targets:"
+	@echo "  make test              Run all pytest tests"
+	@echo "  make test-config       Run config and scheduler tests only"
+	@echo "  make validate-config   Validate data_description.md parsing"
+	@echo "                         Optional: CONFIG_DIR=path/to/config (default: config/)"
+	@echo "  make lint              Placeholder for future linting"
+	@echo ""
+	@echo "Prerequisites: Python virtualenv at .venv/ with dependencies installed"
+
+test:
+	$(PYTEST)
+
+test-config:
+	$(PYTEST) tests/test_config_query_mode.py tests/test_config_sync_schedule.py tests/test_scheduler.py -v
+
+define VALIDATE_SCRIPT
+import os, sys, re, tempfile, shutil
+from pathlib import Path
+
+config_dir = Path(os.environ.get("CONFIG_DIR", "config"))
+config_file = config_dir / "data_description.md"
+if not config_file.exists():
+    print("FAIL: %s not found" % config_file, file=sys.stderr)
+    sys.exit(1)
+
+# Ensure docs/data_description.md exists so Config._find_project_root() works.
+# If CONFIG_DIR points elsewhere, create a temporary symlink.
+docs_path = Path("docs/data_description.md")
+created_symlink = False
+if not docs_path.exists():
+    docs_path.parent.mkdir(parents=True, exist_ok=True)
+    docs_path.symlink_to(config_file.resolve())
+    created_symlink = True
+
+try:
+    from src.config import Config
+    c = Config()
+    names = ", ".join(t.name for t in c.tables)
+    print("OK: parsed %d table(s): %s" % (len(c.tables), names))
+except Exception as e:
+    print("FAIL: %s" % e, file=sys.stderr)
+    sys.exit(1)
+finally:
+    if created_symlink:
+        docs_path.unlink(missing_ok=True)
+endef
+export VALIDATE_SCRIPT
+
+validate-config:
+	@echo "Validating data_description.md in CONFIG_DIR=$(CONFIG_DIR) ..."
+	@CONFIG_DIR=$(CONFIG_DIR) $(PYTHON) -c "$$VALIDATE_SCRIPT"
+
+lint:
+	@echo "Linting not configured yet. Add ruff, flake8, or similar here."

src/config.py

@@ -167,12 +167,13 @@ class TableConfig:
             import re as _re
             valid_schedule = (
                 _re.match(r"^every \d+[mh]$", self.sync_schedule)
-                or _re.match(r"^daily \d{2}:\d{2}$", self.sync_schedule)
+                or _re.match(r"^daily \d{2}:\d{2}(,\d{2}:\d{2})*$", self.sync_schedule)
             )
             if not valid_schedule:
                 raise ValueError(
                     f"Invalid sync_schedule '{self.sync_schedule}' for table {self.id}. "
-                    f"Allowed formats: 'every 15m', 'every 1h', 'daily 05:00'"
+                    f"Allowed formats: 'every 15m', 'every 1h', 'daily 05:00', "
+                    f"'daily 07:00,13:00,18:00'"
                 )
 
         # For partitioned, partition_by must be defined

tests/test_config_sync_schedule.py

@@ -0,0 +1,103 @@
+"""Tests for TableConfig.sync_schedule field validation."""
+
+import pytest
+
+from src.config import TableConfig
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+def _make_table(**overrides) -> TableConfig:
+    """Create a TableConfig with sensible defaults, applying overrides."""
+    defaults = dict(
+        id="test.dataset.table",
+        name="test_table",
+        description="Test",
+        primary_key="id",
+        sync_strategy="full_refresh",
+    )
+    defaults.update(overrides)
+    return TableConfig(**defaults)
+
+
+# ---------------------------------------------------------------------------
+# Tests
+# ---------------------------------------------------------------------------
+class TestSyncScheduleDefault:
+    def test_default_is_none(self):
+        table = _make_table()
+        assert table.sync_schedule is None
+
+
+class TestSyncScheduleValidValues:
+    @pytest.mark.parametrize(
+        "schedule",
+        [
+            "every 15m",
+            "every 1h",
+            "daily 05:00",
+            "daily 07:00,13:00,18:00",
+            "daily 00:00,12:00",
+        ],
+        ids=[
+            "every-15m",
+            "every-1h",
+            "daily-single",
+            "daily-three-times",
+            "daily-two-times",
+        ],
+    )
+    def test_valid_schedule_accepted(self, schedule: str):
+        table = _make_table(sync_schedule=schedule)
+        assert table.sync_schedule == schedule
+
+
+class TestSyncScheduleEdgeCases:
+    def test_every_zero_minutes(self):
+        """every 0m matches the regex -- validation is syntactic, not semantic."""
+        table = _make_table(sync_schedule="every 0m")
+        assert table.sync_schedule == "every 0m"
+
+    def test_daily_2359(self):
+        table = _make_table(sync_schedule="daily 23:59")
+        assert table.sync_schedule == "daily 23:59"
+
+
+class TestSyncScheduleInvalid:
+    @pytest.mark.parametrize(
+        "bad_schedule",
+        [
+            "daily 07:00,13:00,18:00,",  # trailing comma
+            "daily 7:00",                # single-digit hour
+            "daily",                      # missing time
+            "hourly",                     # unsupported keyword
+            "weekly",                     # unsupported keyword
+        ],
+        ids=[
+            "trailing-comma",
+            "single-digit-hour",
+            "daily-no-time",
+            "hourly-keyword",
+            "weekly-keyword",
+        ],
+    )
+    def test_invalid_schedule_raises(self, bad_schedule: str):
+        with pytest.raises(ValueError, match="Invalid sync_schedule"):
+            _make_table(sync_schedule=bad_schedule)
+
+    def test_empty_string_treated_as_none(self):
+        """Empty string is falsy, so validation is skipped (same as None)."""
+        table = _make_table(sync_schedule="")
+        assert table.sync_schedule == ""
+
+    def test_daily_25_accepted_by_regex(self):
+        """25:00 passes regex validation (two digits). Document this behavior."""
+        table = _make_table(sync_schedule="daily 25:00")
+        assert table.sync_schedule == "daily 25:00"
+
+
+class TestSyncScheduleNoneExplicit:
+    def test_explicit_none_accepted(self):
+        table = _make_table(sync_schedule=None)
+        assert table.sync_schedule is None