feat(ready,blocked): Add --parent flag for scoping by epic/bead desce… (#743)

* feat(ready,blocked): Add --parent flag for scoping by epic/bead descendants

Add --parent flag to `bd ready` and `bd blocked` CLI commands and MCP tools
to filter results to all descendants of a specific epic or bead.

## Backward Compatibility

- CLI: New optional --parent flag; existing usage unchanged
- RPC: New `blocked` operation added (was missing); existing operations unchanged
- MCP: New optional `parent` parameter; existing calls work as before
- Storage interface: GetBlockedIssues signature changed to accept WorkFilter
  - All callers updated to pass empty filter for existing behavior
  - Empty WorkFilter{} returns identical results to previous implementation

## Implementation Details

SQLite uses recursive CTE to traverse parent-child hierarchy:

    WITH RECURSIVE descendants AS (
        SELECT issue_id FROM dependencies
        WHERE type = 'parent-child' AND depends_on_id = ?
        UNION ALL
        SELECT d.issue_id FROM dependencies d
        JOIN descendants dt ON d.depends_on_id = dt.issue_id
        WHERE d.type = 'parent-child'
    )
    SELECT issue_id FROM descendants

MemoryStorage implements equivalent recursive traversal with visited-set
cycle protection via collectDescendants helper.

Parent filter composes with existing filters (priority, labels, assignee, etc.)
as an additional WHERE clause - all filters are AND'd together.

## RPC Blocked Support

MCP beads_blocked() existed but daemon client raised NotImplementedError.
Added OpBlocked and handleBlocked to enable daemon RPC path, which was
previously broken. Now both CLI and daemon clients work for blocked queries.

## Changes

- internal/types/types.go: Add ParentID *string to WorkFilter
- internal/storage/sqlite/ready.go: Add recursive CTE for parent filtering
- internal/storage/memory/memory.go: Add getAllDescendants/collectDescendants
- internal/storage/storage.go: Update GetBlockedIssues interface signature
- cmd/bd/ready.go: Add --parent flag to ready and blocked commands
- internal/rpc/protocol.go: Add OpBlocked constant and BlockedArgs type
- internal/rpc/server_issues_epics.go: Add handleBlocked RPC handler
- internal/rpc/client.go: Add Blocked client method
- integrations/beads-mcp/: Add BlockedParams model and parent parameter

## Usage

  bd ready --parent bd-abc              # All ready descendants
  bd ready --parent bd-abc --priority 1 # Combined with other filters
  bd blocked --parent bd-abc            # All blocked descendants

## Testing

Added 4 test cases for parent filtering:
- TestParentIDFilterDescendants: Verifies recursive traversal (grandchildren)
- TestParentIDWithOtherFilters: Verifies composition with priority filter
- TestParentIDWithBlockedDescendants: Verifies blocked issues excluded from ready
- TestParentIDEmptyParent: Verifies empty result for childless parent

* fix: Correct blockedCmd indentation and suppress gosec false positive

- Fix syntax error from incorrect indentation in blockedCmd Run function
- Add nolint:gosec comment for GetBlockedIssues SQL formatting (G201)
  The filterSQL variable contains only parameterized WHERE clauses with
  ? placeholders, not user input

integrations/beads-mcp/src/beads_mcp/bd_daemon_client.py

@@ -11,6 +11,7 @@ from .bd_client import BdClientBase, BdError
 from .models import (
     AddDependencyParams,
     BlockedIssue,
+    BlockedParams,
     CloseIssueParams,
     CreateIssueParams,
     InitParams,
@@ -432,6 +433,9 @@ class BdDaemonClient(BdClientBase):
             args["sort_policy"] = params.sort_policy
         if params.limit:
             args["limit"] = params.limit
+        # Parent filtering (descendants of a bead/epic)
+        if params.parent_id:
+            args["parent_id"] = params.parent_id
 
         data = await self._send_request("ready", args)
         issues_data = json.loads(data) if isinstance(data, str) else data
@@ -451,18 +455,25 @@ class BdDaemonClient(BdClientBase):
             stats_data = {}
         return Stats(**stats_data)
 
-    async def blocked(self) -> List[BlockedIssue]:
+    async def blocked(self, params: Optional[BlockedParams] = None) -> List[BlockedIssue]:
         """Get blocked issues.
 
+        Args:
+            params: Query parameters (optional)
+
         Returns:
             List of blocked issues with their blockers
-
-        Note:
-            This operation may not be implemented in daemon RPC yet
         """
-        # Note: blocked operation may not be in RPC protocol yet
-        # This is a placeholder for when it's added
-        raise NotImplementedError("Blocked operation not yet supported via daemon")
+        params = params or BlockedParams()
+        args: Dict[str, Any] = {}
+        if params.parent_id:
+            args["parent_id"] = params.parent_id
+
+        data = await self._send_request("blocked", args)
+        issues_data = json.loads(data) if isinstance(data, str) else data
+        if issues_data is None:
+            return []
+        return [BlockedIssue(**issue) for issue in issues_data]
 
     async def inspect_migration(self) -> dict[str, Any]:
         """Get migration plan and database state for agent analysis.