📝 docs(codex_skills): normalize markdown formatting

codex/skills/defense-in-depth/SKILL.md

@@ -6,23 +6,28 @@ description: "Defense in depth: add layered validation/guardrails across a data
 # Defense in Depth（分层校验 / 多道防线）
 
 ## When to Use
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 - Auth/data path changes (permissions, roles, ownership checks)
 - Risky inputs (user input, external APIs, files, SQL, commands)
 - Operations that must be safe under retries/concurrency
 - Incidents where we fixed symptoms but not the root class of bugs
 
 ## Inputs（required）
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 - Data path: entrypoints → core logic → side effects (DB/files/network)
 - Threat model: what could go wrong? who can trigger it?
 - Constraints: latency budgets, backward compatibility, rollout plan
 - Verification: how to prove guardrails work (tests, logs, metrics)
 
 ## Procedure（default）
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 1. **Map the Path**
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    - Identify trust boundaries and validation points
    - List invariants that must always hold
 
 2. **Layer Guardrails**
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    - AuthN/AuthZ checks at boundaries (least privilege)
    - Input validation + normalization (reject early)
    - Business invariants (defensive checks with clear errors)
@@ -31,6 +36,7 @@ description: "Defense in depth: add layered validation/guardrails across a data
    - Observability (structured logs, metrics, alerts)
 
 3. **Failure Modes**
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    - Define what happens on invalid input, partial failures, timeouts
    - Ensure errors are actionable and do not leak sensitive info
 
@@ -39,12 +45,14 @@ description: "Defense in depth: add layered validation/guardrails across a data
    - Propose minimal manual verification steps if tests are missing
 
 ## Output Contract（stable）
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 - Path map: trust boundaries + invariants
 - Guardrails: what to add at each layer (with rationale)
 - Risks: what remains and why
 - Verification: exact tests/commands and expected signals
 
 ## Guardrails
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 - Avoid “one big check”; prefer multiple small, well-scoped checks
 - Prefer explicit errors over silent fallback
 - Security checks must not be bypassable via alternate code paths