Scaffold Kissaten Yugure; add M2 day spine, plan and script

Stage 1 (shop scene, customer, siphon brew minigame, serve loop) and the
M2 day spine: day counter, three-phase day, event-driven clock, journal
line, and a SaveState with magic/version/checksum.

Saving to disk is NOT working yet. A cartridge ROM can reach the Disk ROM
only from RAM (both PHYDIO and CALSLT switch page 1 out from under the
caller), and ROMDelayBoot is required so the Disk ROM's INIT runs at all.
With both in place the disk is detected, but sector I/O returns carry-clear
without transferring — proven with a sentinel. Probe now verifies the
buffer actually changed, so a non-working disk degrades to "no save"
rather than corrupting anything. Full findings in the project CLAUDE.md.

Also documented: keyboard reads need interrupt protection (the BIOS ISR
scans the matrix too), and BankedCall must stay off until banked data
exists.

Docs: PLAN.md (ten milestones, per-stage requirements, decision queue),
SCRIPT.md (all four character arcs, 60 beats, checked against the
26-character box), and amendment notes in DESIGN.md.

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

projects/kissaten_yugure/build.bat

@@ -0,0 +1,12 @@
+:: ____________________________
+:: ██▀▀█▀▀██▀▀▀▀▀▀▀█▀▀█        │   ▄▄▄                ▄▄      
+:: ██  ▀  █▄  ▀██▄ ▀ ▄█ ▄▀▀ █  │  ▀█▄  ▄▀██ ▄█▄█ ██▀▄ ██  ▄███
+:: █  █ █  ▀▀  ▄█  █  █ ▀▄█ █▄ │  ▄▄█▀ ▀▄██ ██ █ ██▀  ▀█▄ ▀█▄▄
+:: ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀────────┘                 ▀▀
+::  by Guillaume 'Aoineko' Blanchard under CC BY-SA license
+::────────────────────────────────────────────────────────────────────
+@echo off
+
+cls
+
+..\..\tools\build\Node\node.exe ..\..\engine\script\js\build.js %1 %2 %3 %4 %5 %6 %7 %8 %9