TODO: backlog of bugs + long-term items, milestones live in REWORK_PLAN

TODO = backlog from user. REWORK_PLAN = milestones/infra. M4 (dead-not-
skipped) is a milestone, stays in REWORK_PLAN. Removed false 'bugs only'
and M4 references from TODO header.

TODO.md

@@ -1,7 +1,7 @@
 # TODO
 
-Confirmed bugs found via testing. M4 (dead-not-skipped) lives in
-REWORK_PLAN.md — not here. This file = bugs only.
+Backlog of bugs + long-term items, from user. Milestones live in
+REWORK_PLAN.md.
 
 ## Confirmed bugs (tests written, NOT fixed)