feat: add 33 retrieval_* i18n keys for error distinction and recovery UI

Adds all retrieval state labels, button text, warning messages, and
descriptive copy in English and Chinese under the retrieval_* prefix.

Prepares i18n foundation for search domain (8 states) and build domain
(10 states) per PRD #57 and issue #62.

paperforge/plugin/src/i18n.ts

@@ -283,6 +283,40 @@ const LANG: Record<string, Record<string, string>> = {
     version_compare_title: "{vA} vs {vB}",
     version_compare_paragraphs: "{n} paragraphs changed",
     version_error_read: "Cannot read version data",
+    retrieval_search_placeholder: "Search papers... (@ for deep search)",
+    retrieval_search_placeholder_deep: "Search papers via deep retrieval...",
+    retrieval_search_idle_hint: "Type to search metadata, or start with @ for deep semantic search",
+    retrieval_searching_metadata: "Searching metadata...",
+    retrieval_searching_deep: "Running deep search...",
+    retrieval_search_cancel: "Cancel",
+    retrieval_results_count: "{n} result{s}",
+    retrieval_empty: "No matching papers found.",
+    retrieval_empty_tips: "Try broader terms or @ deep search.",
+    retrieval_vectors_not_built: "Vectors Not Built",
+    retrieval_vectors_not_built_desc: "Vector index has not been built. Search requires a built vector index.",
+    retrieval_open_vector_settings: "Open Vector Settings",
+    retrieval_backend_unavailable: "Backend Unavailable",
+    retrieval_backend_unavailable_desc: "The Python CLI search backend is not responding.",
+    retrieval_run_doctor: "Run Doctor",
+    retrieval_retry: "Retry",
+    retrieval_timeout_title: "Search Timed Out",
+    retrieval_timeout_desc: "The search took too long. You can retry or try a simpler query.",
+    retrieval_model_changed: "Model Changed",
+    retrieval_model_changed_desc: "The embedding model has changed since vectors were built. Rebuilding is required.",
+    retrieval_rebuild_vectors: "Rebuild Vectors",
+    retrieval_internal_error: "An internal error occurred. Check the console for details.",
+    retrieval_build_idle: "Vectors not yet built",
+    retrieval_build_ready: "Vectors ready",
+    retrieval_build_stopping: "Stopping...",
+    retrieval_build_stopped: "Build stopped. Resume to continue.",
+    retrieval_build_failed: "Build failed",
+    retrieval_build_stale: "Previous build was interrupted. Resume to continue.",
+    retrieval_build_deps_missing: "Dependencies not installed",
+    retrieval_build_runtime_mismatch: "Plugin and CLI versions differ",
+    retrieval_stop: "Stop",
+    retrieval_force_rebuild: "Force Rebuild",
+    retrieval_rebuild_warning: "Rebuild will replace {n} existing chunk(s). Continue?",
+    retrieval_no_python: "No Python found. Check Installation tab.",
   },
 
   zh: {
@@ -543,6 +577,40 @@ const LANG: Record<string, Record<string, string>> = {
     version_compare_title: "{vA} vs {vB}",
     version_compare_paragraphs: "{n} 段有变化",
     version_error_read: "无法读取版本数据",
+    retrieval_search_placeholder: "搜索论文... (@ 进行深度搜索)",
+    retrieval_search_placeholder_deep: "通过深度检索搜索论文...",
+    retrieval_search_idle_hint: "输入关键字搜索元数据，或以 @ 开头进行深度语义搜索",
+    retrieval_searching_metadata: "正在搜索元数据...",
+    retrieval_searching_deep: "正在运行深度搜索...",
+    retrieval_search_cancel: "取消",
+    retrieval_results_count: "找到 {n} 条结果",
+    retrieval_empty: "未找到匹配的论文。",
+    retrieval_empty_tips: "尝试更宽泛的关键词，或使用 @ 进行深度搜索。",
+    retrieval_vectors_not_built: "向量索引未构建",
+    retrieval_vectors_not_built_desc: "向量索引尚未构建，搜索需要先构建向量索引。",
+    retrieval_open_vector_settings: "打开向量设置",
+    retrieval_backend_unavailable: "后端不可用",
+    retrieval_backend_unavailable_desc: "Python CLI 搜索后端无响应。",
+    retrieval_run_doctor: "运行诊断",
+    retrieval_retry: "重试",
+    retrieval_timeout_title: "搜索超时",
+    retrieval_timeout_desc: "搜索耗时过长。你可以重试，或尝试简化查询。",
+    retrieval_model_changed: "模型已更换",
+    retrieval_model_changed_desc: "嵌入模型已更换，需要重建向量。",
+    retrieval_rebuild_vectors: "重建向量",
+    retrieval_internal_error: "发生内部错误。请查看控制台了解详情。",
+    retrieval_build_idle: "向量索引尚未构建",
+    retrieval_build_ready: "向量索引就绪",
+    retrieval_build_stopping: "正在停止…",
+    retrieval_build_stopped: "构建已停止。点击继续以恢复。",
+    retrieval_build_failed: "构建失败",
+    retrieval_build_stale: "上次构建被中断。点击继续以恢复。",
+    retrieval_build_deps_missing: "依赖未安装",
+    retrieval_build_runtime_mismatch: "插件与 CLI 版本不匹配",
+    retrieval_stop: "停止",
+    retrieval_force_rebuild: "强制重建",
+    retrieval_rebuild_warning: "重建将替换 {n} 个已有的 chunk。是否继续？",
+    retrieval_no_python: "未找到 Python。请查看安装标签页。",
   },
 };