Add MCP tools for migration inspection (bd-627d Phase 3)

- Add inspect_migration() tool - calls bd migrate --inspect --json
- Add get_schema_info() tool - calls bd info --schema --json
- Implements abstract methods in BdClientBase
- CLI client calls commands directly
- Daemon client raises NotImplementedError (rare admin commands)

Phase 3 complete. Agents can now inspect migrations via MCP before running them.

Amp-Thread-ID: https://ampcode.com/threads/T-de7e1141-87ac-4b4a-9cea-1b7bc4d51da9
Co-authored-by: Amp <amp@ampcode.com>

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

@@ -18,7 +18,9 @@ from beads_mcp.tools import (
     beads_blocked,
     beads_close_issue,
     beads_create_issue,
+    beads_get_schema_info,
     beads_init,
+    beads_inspect_migration,
     beads_list_issues,
     beads_quickstart,
     beads_ready_work,
@@ -512,6 +514,39 @@ async def debug_env(workspace_root: str | None = None) -> str:
     return "".join(info)
 
 
+@mcp.tool(
+    name="inspect_migration",
+    description="Get migration plan and database state for agent analysis.",
+)
+@with_workspace
+async def inspect_migration(workspace_root: str | None = None) -> dict:
+    """Get migration plan and database state for agent analysis.
+    
+    AI agents should:
+    1. Review registered_migrations to understand what will run
+    2. Check warnings array for issues (missing config, version mismatch)
+    3. Verify missing_config is empty before migrating
+    4. Check invariants_to_check to understand safety guarantees
+    
+    Returns migration plan, current db state, warnings, and invariants.
+    """
+    return await beads_inspect_migration()
+
+
+@mcp.tool(
+    name="get_schema_info",
+    description="Get current database schema for inspection.",
+)
+@with_workspace
+async def get_schema_info(workspace_root: str | None = None) -> dict:
+    """Get current database schema for inspection.
+    
+    Returns tables, schema version, config, sample issue IDs, and detected prefix.
+    Useful for verifying database state before migrations.
+    """
+    return await beads_get_schema_info()
+
+
 async def async_main() -> None:
     """Async entry point for the MCP server."""
     await mcp.run_async(transport="stdio")