Delete PLAN.md — HANDOFF is the only planning document

Everything it specified shipped long ago, and the parts still worth knowing are
already folded into HANDOFF. Keeping a stale plan around only invites a future
session to treat it as live spec.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

HANDOFF.md

@@ -1,8 +1,9 @@
 # HANDOFF — Splatter Tennis
 
-**This file is the source of truth.** `PLAN.md` is historical (the original build plan, all
-shipped); `POLISH-PLAN.md` is deleted — everything it specified is done and recorded below.
-Also auto-loaded: `~/.claude/projects/.../memory/splatter-tennis-history.md` for the long history.
+**This file is the only planning document.** `PLAN.md` and `POLISH-PLAN.md` are deleted —
+everything they specified is shipped, and what still matters from them is recorded below. For the
+long history, `~/.claude/projects/.../memory/splatter-tennis-history.md` is auto-loaded; for the
+detail of any individual change, read the git log.
 
 Last updated 2026-07-27 after Oliver's 35-game retest. **Open issues are at the bottom — start there.**