Append a "Phase 2 considerations" section capturing the two
unresolved architecture debates Linus and Jobs surfaced in T1
review:
- Linus: drop the status->phase TRIGGER in favour of explicit
dual-write at every call site. Deferred to Phase 2 with explicit
rationale (existing two-layer guard + 5-commit blast radius).
- Jobs: flip reads from legacy columns to phase / task_leases.
Deferred until B5 eval harness can baseline agent behaviour.
Also records the four entry criteria for Phase 2 and the four gates
for Phase 3 drop-old-columns, so the next iteration has a concrete
checklist rather than a re-argument.
ZacharyZhang-NY