Support querying sessions by cell index and notebookURI

[jlewi]

A convenient way to be able to find relevant sessions would be to query by selected cell index and notebook URI.

This would make it easier to find sessions associated with a particular cell.

[jlewi]

Here's a Google Cloud Logging Query that can do it

gcloud logging read 'logName="projects/foyle-dev/logs/foyle" AND jsonPayload.context.notebookUri="file:///Users/jlewi/git_worklog/foyle/2024_10_01_blank_cells.md" AND  jsonPayload.context.selected=10' --limit 20 --format=json

Note this query doesn't work if selected=0 because the proto serializer doesn't include default values when serializing to JSON.

foyle/app/pkg/agent/agent.go

Line 333 in 238e04f

log.Info("Received full context", "contextId", req.GetContextId(), logs.ZapProto("context", req.GetFullContext()))

We could potentially change that.

If we stored the session proto as JSON in sqlite then we should be able to use sqlite's JSON functionality to run a similar query.