Remove unused files in @kbn/observability-ai-assistant-app-plugin (dead code cleanup) (elastic#266813)

## Summary

Removes **10 unused source files** (168 LoC) from
`@kbn/observability-ai-assistant-app-plugin`, owned by
`@elastic/obs-ai-team`. All verified to have **zero static importers**
anywhere in the repo.

This is one slice of a broader sweep across the codebase removing **399
files / 18.5k LoC** of dead code. Co-PRs cover the other ~28 teams'
slices. The methodology is in elastic#266635 (skill PR).

## Files removed

See the diff. Removals span the package — common shapes include:

- Orphan barrel `index.ts` files where consumers consistently
deep-import the sibling modules directly.
- Dead React components, hooks, route handlers, or test helpers no
longer referenced anywhere.

## Verification

For every file:

1. **`knip` flagged it as unreachable** from the package's declared
entry points (`server/index.ts`, `public/index.ts`, `common/index.ts`,
plus deep-import-derived entries).
2. **Resolve-aware import scan** confirmed zero importers across the
repo (Node-style: `<base>.ts`, `<base>.tsx`, `<base>/index.ts`,
`<base>/index.tsx`).
3. **Package-id deep-import grep** for
`@kbn/observability-ai-assistant-app-plugin/<sub>` references from other
packages.
4. **`jest.mock()` string scan** for test mocks pointing at the path.
5. **Type-check passes** (`node scripts/type_check --project
x-pack/solutions/observability/plugins/observability_ai_assistant_app/tsconfig.json`).

## Patterns observed (for context)

The most common dead-code shapes in this slice:

- **Orphan barrel `index.ts`** that re-exports from siblings — the
commonest shape across the cleanup.
- Other patterns vary by package (dead React components, dead route
handlers, dead test fixtures).

The full pattern catalog (across all teams) is in elastic#266635.

🤖 Generated by an AI agent following a verification recipe at
`.agents/skills/dead-code-cleanup/SKILL.md` (PR elastic#266635).

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rudolf

x-pack/platform/plugins/private/translations/translations/de-DE.json

@@ -35231,8 +35231,6 @@
     "xpack.observabilityAiAssistant.eisKnowledgeBase.dismissButton": "Verwerfen",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.learnMoreButton": "Weitere Informationen",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.title": "Elastic Inference Service (EIS) ist jetzt verfügbar",
-    "xpack.observabilityAiAssistant.experimentalTitle": "Technische Vorschau",
-    "xpack.observabilityAiAssistant.experimentalTooltip": "Diese Funktionalität befindet sich in der technischen Vorschau und kann in einer zukünftigen Version geändert oder vollständig entfernt werden. Elastic wird sich bemühen, alle Probleme zu beheben, aber die Features in der technischen Vorschau unterliegen nicht dem Support-SLA der offiziellen GA-Features.",
     "xpack.observabilityAiAssistant.failedLoadingResponseText": "Antwort konnte nicht geladen werden",
     "xpack.observabilityAiAssistant.failedToLoadResponse": "Antwort vom KI-Assistenten konnte nicht geladen werden",
     "xpack.observabilityAiAssistant.featureRegistry.featureName": "KI-Assistent für Observability",

x-pack/platform/plugins/private/translations/translations/fr-FR.json

@@ -35168,8 +35168,6 @@
     "xpack.observabilityAiAssistant.eisKnowledgeBase.dismissButton": "Rejeter",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.learnMoreButton": "En savoir plus",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.title": "Elastic Inference Service (EIS) désormais disponible",
-    "xpack.observabilityAiAssistant.experimentalTitle": "Version d'évaluation technique",
-    "xpack.observabilityAiAssistant.experimentalTooltip": "Cette fonctionnalité est en version d'évaluation technique et pourra être modifiée ou retirée complètement dans une future version. Elastic s'efforcera de corriger tout problème, mais les fonctionnalités des versions d'évaluation technique ne sont pas soumises aux SLA de support des fonctionnalités officielles en disponibilité générale.",
     "xpack.observabilityAiAssistant.failedLoadingResponseText": "Échec de chargement de la réponse",
     "xpack.observabilityAiAssistant.failedToLoadResponse": "Échec du chargement d'une réponse de l'assistant d'intelligence artificielle",
     "xpack.observabilityAiAssistant.featureRegistry.featureName": "Assistant d'intelligence artificielle d'Observability",

x-pack/platform/plugins/private/translations/translations/ja-JP.json

@@ -35351,8 +35351,6 @@
     "xpack.observabilityAiAssistant.eisKnowledgeBase.dismissButton": "閉じる",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.learnMoreButton": "詳しくはこちら",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.title": "Elastic Inference Service（EIS）が利用可能になりました",
-    "xpack.observabilityAiAssistant.experimentalTitle": "テクニカルプレビュー",
-    "xpack.observabilityAiAssistant.experimentalTooltip": "この機能はテクニカルプレビュー中であり、将来のリリースでは変更されたり完全に削除されたりする場合があります。Elasticはすべての問題の修正に努めますが、テクニカルプレビュー中の機能には正式なGA機能のサポートSLAが適用されません。",
     "xpack.observabilityAiAssistant.failedLoadingResponseText": "応答の読み込みに失敗しました",
     "xpack.observabilityAiAssistant.failedToLoadResponse": "AIアシスタントからの応答を読み込めませんでした",
     "xpack.observabilityAiAssistant.featureRegistry.featureName": "オブザーバビリティAI Assistant",

x-pack/platform/plugins/private/translations/translations/zh-CN.json

@@ -35353,8 +35353,6 @@
     "xpack.observabilityAiAssistant.eisKnowledgeBase.dismissButton": "关闭",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.learnMoreButton": "了解详情",
     "xpack.observabilityAiAssistant.eisKnowledgeBase.title": "Elastic Inference Service (EIS) 现已推出",
-    "xpack.observabilityAiAssistant.experimentalTitle": "技术预览",
-    "xpack.observabilityAiAssistant.experimentalTooltip": "此功能处于技术预览状态，在未来版本中可能会更改或完全移除。Elastic 将努力修复任何问题，但处于技术预览状态的功能不受正式 GA 功能支持 SLA 的约束。",
     "xpack.observabilityAiAssistant.failedLoadingResponseText": "无法加载响应",
     "xpack.observabilityAiAssistant.failedToLoadResponse": "无法加载来自 AI 助手的响应",
     "xpack.observabilityAiAssistant.featureRegistry.featureName": "Observability AI 助手",

x-pack/solutions/observability/plugins/observability_ai_assistant_app/moon.yml

@@ -86,8 +86,6 @@ dependsOn:
   - '@kbn/i18n-react'
   - '@kbn/utility-types'
   - '@kbn/alerts-ui-shared'
-  - '@kbn/traced-es-client'
-  - '@kbn/licensing-types'
   - '@kbn/utility-types-jest'
   - '@kbn/zod'
   - '@kbn/connector-schemas'