fix the writing of graphs in graphql

[ljeub-pometry]

Currently writing a graph to disk from graphql causes the vector database/indexes to be lost because the folder gets overwritten. This also fails on windows because the vector database is open

[ljeub-pometry]

rough design for making the graphs atomically swappable

[ljeub-pometry]

Check that upload_graph doesn't block the server while the upload is in progress

[ljeub-pometry]

rename inner .raph to .meta