Add Xiapi outer siege chapter

docs/roadmap.md

@@ -31,12 +31,13 @@ Build a small complete tactical RPG loop that can grow into a longer Romance of
 - Ninth battle Xuzhou gate night raid, opening Lu Bu's refuge and the internal instability that leads toward the loss of Xu Province
 - Tenth battle Xuzhou breakout, covering Zhang Fei's mistake, the loss of Xu Province to Lu Bu, and the retreat toward Cao Cao's shadow
 - Eleventh battle Xudu refuge road, opening Liu Bei's uneasy service under Cao Cao through a Yuan Shu remnant test battle
+- Twelfth battle Xiapi outer siege, putting Liu Bei under Cao Cao's command against Lu Bu while preserving Liu Bei's independent motive and camp tension
 - Tactical sortie preparation panel with battle-specific sortie limits, recommended officers with reasons, class role, named equipment, core stats, bond partner, next-map terrain suitability, deployment preview, formation roles, active bond count, and readiness advice for each deployable officer
-- Flow verification script from title through the eleventh battle victory, recruit sortie selection, and camp save state
+- Flow verification script from title through the twelfth battle victory, recruit sortie selection, and camp save state
 
 ## Next Steps
 
-1. Continue into Liu Bei's tense service under Cao Cao, then build toward the break from Cao Cao
+1. Continue the Xiapi siege toward Lu Bu's fall, then build toward Liu Bei's break from Cao Cao
 2. Add a chapter/progress view so long campaign arcs are easier to read between battles
 3. Apply treasure equipment effects to damage, defense, recovery, and command rules
 4. Add more recruitable officers as the campaign moves toward Cao Cao, Yuan Shao, Liu Biao, and Zhuge Liang