Insert four new phases between the call prune (5) and the old http fix:
- Phase 6: Core stream unification (BiStream as handler leaf, ADR-092)
- Phase 7: TTY control-channel bidirectionality fix (STREAM_CTRL_IN/OUT)
- Phase 8: Channels spec cleanup (8-byte wire format, no stream_type)
- Phase 9: HTTP fix — drop QuicStream wrapper (now unnecessary after BiStream)
The old Phase 6 (http fix, deferred) is replaced — BiStream makes the
QuicStream wrapper dead code. Total: 10 phases (0-9).