feat: add run replay for archetype effectiveness analysis

- archeflow-decision.sh records decision points during runs
- archeflow-replay.sh: timeline, whatif, compare commands
- What-if replay with adjustable archetype weights
- /af-replay skill for interactive use
- Tests in archeflow-replay.bats

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 All notable changes to ArcheFlow are documented in this file.
 
+## [0.9.0] -- 2026-04-06
+
+### Added
+- Run replay: `decision.point` events via `archeflow-decision.sh`; `archeflow-replay.sh` with `timeline`, `whatif` (weighted archetype weights + threshold), and `compare`; skill `af-replay`; DAG labels for `decision.point`.
+
 ## [0.7.0] -- 2026-04-04
 
 ### Added