Fixed 7 issues found during self-audit:
1. §4.2.4: stale reference to '$4.2.5 旧内容' (that section is now Secrets, not healthcheck). Pointed to §10.4 instead.
2. §6 Step 3: wrong cross-reference §10.2 (which is Secret strategy). Should be §10.1 (image registry).
3. §5 directory tree: hpa was duplicated in both gateway/ and hpa/. Unified to single hpa/ directory.
4. §5 directory tree: .gitignore was placed under k8s/. Moved indication to repo root with clearer comment.
5. §5 principles: added '关注点分离' (separation of concerns) for HPA/Ingress/Secret dirs.
6. §6 Step 4: title was '灰度切换' (gradual cutover) but content said 'single namespace, all traffic switched at once'. Renamed to '流量切换'.
7. §6 Step 4 + Step 5: sequence sync step was duplicated with unclear timing. Consolidated into Step 4 as a hard blocker. Step 5 now just stops VM.
8. §4.4 (data layer multi-tenancy): duplicated §11.4.4. Deleted §4.4; kept pointer in §4.3.
9. §3 comparison table: '后续按组隔离成本' for B was undersold as 'low (helm values)'. Corrected to '中' with reference to §11.5 (~2-3 months).
Advisory items left as-is (not blocking): §1.1 '腰部明星' line, §11.4.3 '方式 2' detail.
zheng020
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