Quartz's leaveGroup was returning `proposal.toTlsBytes()` and
publishing that raw on kind:445. That's not a valid MLS message
— it's just the proposal struct with no FramedContent / MlsMessage
framing — and even if it parsed, mdk/openmls would only STAGE the
proposal. The target never actually leaves the tree until someone
commits with that proposal.
MIP-03 explicitly allows non-admins to commit a SelfRemove-only
commit, so amy can produce a proper committable kind:445 herself
after the self-demote. Replace `selfRemove()` (returned raw bytes)
with `selfRemoveCommit()` which adds the proposal to the pending
set and runs the standard `commit()` path. Plumb the resulting
CommitResult through MarmotManager.leaveGroup so the outer
encryption uses `preCommitExporterSecret` (the epoch we're
leaving, which is the one every existing member still has).
This finally propagates amy's leave to B in test 11.
https://claude.ai/code/session_1469d7f4-bb66-4ffa-a44d-1dfa4b526484
Claude
b01ee5336a