The standalone military source no longer has getTrack, so the MCP
get_aircraft_track tool threw a TypeError and MCP advised a retry. It
now returns an `unsupported` ToolError when the selected feed has no
getTrack, while custom sources that supply history still work. Tests
cover the default composition through the catalog and MCP.
Also drop the unused epoch import and update the CURRENT-STATE track
sections to describe local trails and 503 history_unavailable.
Co-Authored-By: Claude Opus 5.5 <[email protected]>