fix(problem-deploy): make disruptions work in Lite mode (same-account injection)

[susumutomita]

Summary

Lite mode で「障害を注入したのにフロントエンドがダウンしない」(fire は記録されるが注入が silently no-op) を修正します。Closes #1710。原因は 2 つの連動した問題でした。

1. resolveDeployment が cross-account フィールドを必須にしていた: competitorRoleArn + externalIdParameterName が両方無いと undefined（→ no_deployment → no-op）。Lite は same-account deploy でどちらも持たないため、Lite の fire は常に no-op。→ 両フィールドを optional にし、COMPLETE な same-account row は target を返す。executor は既存の assumeCompetitorRole の same-account 経路（双方 absent → undefined creds）で Lambda 自身の credentials を使う。

2. executor Lambda の role に ssm:SendCommand が無かった: 注入は assumed の競技者 AdministratorAccess role 経由という設計（ADR-031）。Lite には assume 先が無いので、ssm:SendCommand を Lambda 自身の role に、同一アカウントの instance + 標準 shell document（AWS-RunShellScript / SSM-SessionManagerRunShell）に scope して付与。SaaS は従来通り assumed role で注入するため本 grant は不使用。

lambda-invoke / cfn-stack-update kind の Lite 対応は同様の own-role grant が必要（follow-up）。ssm-run-command（サンプル red team）は本 PR で動作。

反映

problem-deploy backend の再デプロイで executor Lambda が更新されます。

Test plan

• disruption-executor-store.test.ts: cross-account フィールド無しの Lite COMPLETE row が same-account target を返すことを pin（旧 "skip" テストを置換）。
• disruption-executor-lambda.test.ts: 自前 role に ssm:SendCommand が付き同一アカウント instance + AWS-RunShellScript に scope、Invoke/UpdateStack は依然無いことを pin。
• 既存 executor / contract テスト green。make harness / make before-commit（synth 含む）green。

Regression analysis

• SaaS (cross-account): 両フィールドが揃えば従来通り target を返し、注入は assumed Admin role 経由のまま（own role の SendCommand 不使用）。挙動不変。
• IAM scope: ssm:SendCommand は same-account（${stack.account}）の instance + 標準 shell document に限定。Lite は単一テナント=organizer 自身の account のためブラスト半径は閉じる。

Physical impact

• AWS::IAM::Policy（DisruptionExecutor Lambda role）に ssm:SendCommand ステートメント 追加 = UPDATE（in-place）。Lambda code 更新 = UPDATE。新規/削除リソースなし。

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 96943f1e-bbe4-453b-99e4-c5da078ec800

📥 Commits

Reviewing files that changed from the base of the PR and between f399603 and ab28102.

📒 Files selected for processing (5)

• infrastructure/lib/problem-deploy/disruption-executor-lambda.ts
• infrastructure/lib/problem-deploy/handlers/disruption-executor-handler/execute.ts
• infrastructure/lib/problem-deploy/handlers/disruption-executor-handler/executor-store.ts
• infrastructure/test/problem-deploy/disruption-executor-lambda.test.ts
• infrastructure/test/problem-deploy/disruption-executor-store.test.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/1710-lite-mode-disruptions

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.75%. Comparing base (f399603) to head (ab28102).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1711   +/-   ##
=======================================
  Coverage   92.75%   92.75%           
=======================================
  Files         434      434           
  Lines       11896    11899    +3     
  Branches     3654     3655    +1     
=======================================
+ Hits        11034    11037    +3     
  Misses        295      295           
  Partials      567      567           

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