The last git calls the server waited for

Two checks still made Obeya's server stop and wait for git, freezing every page meanwhile. The first asked whether a workstream's landed work had reached the copy of the main branch that plan docs are read from, again on every reading of the plan docs. The second read the main branch's CLAUDE.md for each review card's agent as it started. Both now run in the background and are kept until the main branch moves. With 8 such workstreams, 20 readings of the plan docs used to stall the server for about 0.7 s in total; now they don't stall it at all.