v2.9.0: domain-level session + assertion-driven delivery + MCP v0.8.0

- Principle #5: no skipping degradation tiers (anti AI strategic surrender)
- Phase 0 step 4: start_reverse_session() zero-arg domain auto-detect
- Phase 0.5.-1: domain assertion reverify before fingerprint matching
- Phase 5: assertion-driven delivery (verify_against_session + add_assertion)
- Core weapon: MCP v0.8.0 (78 tools), domain session + assertion section
- Error handling: AI surrender degradation tier table (L1-L6)
- Experience rules: 40 -> 46 (domain persistence / reverify / assertion ROI)
- New: references/domain-session-guide.md
- New: CHANGELOG_v2.9.0.md
- Skip v2.8.0 (process-level session design rejected)

.gitignore

@@ -6,5 +6,8 @@ node_modules/
 # 私有域名映射（不纳入版本控制）
 cases/_private_mapping.json
 
+# 域级 Session 档案（含运行时状态，不纳入版本控制）
+cases/_session_archives/
+
 # Claude 配置目录
 .claude/