feat: implement XER MCP Server with 9 schedule query tools

Implement complete MCP server for parsing Primavera P6 XER files and
exposing schedule data through MCP tools. All 4 user stories complete.

Tools implemented:
- load_xer: Parse XER files into SQLite database
- list_activities: Query activities with pagination and filtering
- get_activity: Get activity details by ID
- list_relationships: Query activity dependencies
- get_predecessors/get_successors: Query activity relationships
- get_project_summary: Project overview with counts
- list_milestones: Query milestone activities
- get_critical_path: Query driving path activities

Features:
- Tab-delimited XER format parsing with pluggable table handlers
- In-memory SQLite database for fast queries
- Pagination with 100-item default limit
- Multi-project file support with project selection
- ISO8601 date formatting
- NO_FILE_LOADED error handling for all query tools

Test coverage: 81 tests (contract, integration, unit)

src/xer_mcp/parser/table_handlers/__init__.py

@@ -0,0 +1,27 @@
+"""XER table handlers module."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+from xer_mcp.parser.table_handlers.calendar import CalendarHandler
+from xer_mcp.parser.table_handlers.project import ProjectHandler
+from xer_mcp.parser.table_handlers.projwbs import ProjwbsHandler
+from xer_mcp.parser.table_handlers.task import TaskHandler
+from xer_mcp.parser.table_handlers.taskpred import TaskpredHandler
+
+# Registry mapping table names to handlers
+TABLE_HANDLERS: dict[str, type[TableHandler]] = {
+    "PROJECT": ProjectHandler,
+    "TASK": TaskHandler,
+    "TASKPRED": TaskpredHandler,
+    "PROJWBS": ProjwbsHandler,
+    "CALENDAR": CalendarHandler,
+}
+
+__all__ = [
+    "CalendarHandler",
+    "ProjectHandler",
+    "ProjwbsHandler",
+    "TABLE_HANDLERS",
+    "TableHandler",
+    "TaskHandler",
+    "TaskpredHandler",
+]

src/xer_mcp/parser/table_handlers/base.py

@@ -0,0 +1,30 @@
+"""Base class for XER table handlers."""
+
+from abc import ABC, abstractmethod
+
+
+class TableHandler(ABC):
+    """Abstract base class for XER table handlers.
+
+    Each handler is responsible for parsing a specific table type
+    from the XER file and returning structured data.
+    """
+
+    @property
+    @abstractmethod
+    def table_name(self) -> str:
+        """Return the XER table name this handler processes (e.g., 'PROJECT', 'TASK')."""
+        ...
+
+    @abstractmethod
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a single row of data from the XER file.
+
+        Args:
+            fields: List of column names from the %F line
+            values: List of values from the %R line
+
+        Returns:
+            Dictionary of parsed data, or None if the row should be skipped
+        """
+        ...

src/xer_mcp/parser/table_handlers/calendar.py

@@ -0,0 +1,32 @@
+"""CALENDAR table handler."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+
+
+class CalendarHandler(TableHandler):
+    """Handler for CALENDAR table in XER files."""
+
+    @property
+    def table_name(self) -> str:
+        return "CALENDAR"
+
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a CALENDAR row."""
+        if len(values) < len(fields):
+            values = values + [""] * (len(fields) - len(values))
+
+        data = dict(zip(fields, values, strict=False))
+
+        # Parse numeric fields
+        day_hr_str = data.get("day_hr_cnt", "")
+        day_hr = float(day_hr_str) if day_hr_str else None
+
+        week_hr_str = data.get("week_hr_cnt", "")
+        week_hr = float(week_hr_str) if week_hr_str else None
+
+        return {
+            "clndr_id": data.get("clndr_id", ""),
+            "clndr_name": data.get("clndr_name", ""),
+            "day_hr_cnt": day_hr,
+            "week_hr_cnt": week_hr,
+        }

src/xer_mcp/parser/table_handlers/project.py

@@ -0,0 +1,38 @@
+"""PROJECT table handler."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+
+
+def convert_date(date_str: str | None) -> str | None:
+    """Convert XER date format to ISO8601.
+
+    XER format: "YYYY-MM-DD HH:MM"
+    ISO8601 format: "YYYY-MM-DDTHH:MM:SS"
+    """
+    if not date_str or date_str.strip() == "":
+        return None
+    # Replace space with T and add seconds
+    return date_str.replace(" ", "T") + ":00"
+
+
+class ProjectHandler(TableHandler):
+    """Handler for PROJECT table in XER files."""
+
+    @property
+    def table_name(self) -> str:
+        return "PROJECT"
+
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a PROJECT row."""
+        if len(values) < len(fields):
+            # Pad with empty strings if needed
+            values = values + [""] * (len(fields) - len(values))
+
+        data = dict(zip(fields, values, strict=False))
+
+        return {
+            "proj_id": data.get("proj_id", ""),
+            "proj_short_name": data.get("proj_short_name", ""),
+            "plan_start_date": convert_date(data.get("plan_start_date")),
+            "plan_end_date": convert_date(data.get("plan_end_date")),
+        }

src/xer_mcp/parser/table_handlers/projwbs.py

@@ -0,0 +1,26 @@
+"""PROJWBS table handler."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+
+
+class ProjwbsHandler(TableHandler):
+    """Handler for PROJWBS (WBS) table in XER files."""
+
+    @property
+    def table_name(self) -> str:
+        return "PROJWBS"
+
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a PROJWBS row."""
+        if len(values) < len(fields):
+            values = values + [""] * (len(fields) - len(values))
+
+        data = dict(zip(fields, values, strict=False))
+
+        return {
+            "wbs_id": data.get("wbs_id", ""),
+            "proj_id": data.get("proj_id", ""),
+            "parent_wbs_id": data.get("parent_wbs_id", ""),
+            "wbs_short_name": data.get("wbs_short_name", ""),
+            "wbs_name": data.get("wbs_name") or None,
+        }

src/xer_mcp/parser/table_handlers/task.py

@@ -0,0 +1,43 @@
+"""TASK table handler."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+from xer_mcp.parser.table_handlers.project import convert_date
+
+
+class TaskHandler(TableHandler):
+    """Handler for TASK table in XER files."""
+
+    @property
+    def table_name(self) -> str:
+        return "TASK"
+
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a TASK row."""
+        if len(values) < len(fields):
+            values = values + [""] * (len(fields) - len(values))
+
+        data = dict(zip(fields, values, strict=False))
+
+        # Parse driving_path_flag (Y/N -> bool)
+        driving_flag = data.get("driving_path_flag", "N")
+        driving_path = driving_flag.upper() == "Y" if driving_flag else False
+
+        # Parse total_float_hr_cnt
+        float_str = data.get("total_float_hr_cnt", "")
+        total_float = float(float_str) if float_str else None
+
+        return {
+            "task_id": data.get("task_id", ""),
+            "proj_id": data.get("proj_id", ""),
+            "wbs_id": data.get("wbs_id") or None,
+            "task_code": data.get("task_code", ""),
+            "task_name": data.get("task_name", ""),
+            "task_type": data.get("task_type", ""),
+            "status_code": data.get("status_code") or None,
+            "target_start_date": convert_date(data.get("target_start_date")),
+            "target_end_date": convert_date(data.get("target_end_date")),
+            "act_start_date": convert_date(data.get("act_start_date")),
+            "act_end_date": convert_date(data.get("act_end_date")),
+            "total_float_hr_cnt": total_float,
+            "driving_path_flag": driving_path,
+        }

src/xer_mcp/parser/table_handlers/taskpred.py

@@ -0,0 +1,31 @@
+"""TASKPRED table handler."""
+
+from xer_mcp.parser.table_handlers.base import TableHandler
+
+
+class TaskpredHandler(TableHandler):
+    """Handler for TASKPRED (relationships) table in XER files."""
+
+    @property
+    def table_name(self) -> str:
+        return "TASKPRED"
+
+    def parse_row(self, fields: list[str], values: list[str]) -> dict | None:
+        """Parse a TASKPRED row."""
+        if len(values) < len(fields):
+            values = values + [""] * (len(fields) - len(values))
+
+        data = dict(zip(fields, values, strict=False))
+
+        # Parse lag_hr_cnt
+        lag_str = data.get("lag_hr_cnt", "0")
+        lag_hr = float(lag_str) if lag_str else 0.0
+
+        return {
+            "task_pred_id": data.get("task_pred_id", ""),
+            "task_id": data.get("task_id", ""),
+            "pred_task_id": data.get("pred_task_id", ""),
+            "proj_id": data.get("proj_id", ""),
+            "pred_type": data.get("pred_type", ""),
+            "lag_hr_cnt": lag_hr,
+        }