feat: server-side GitHub search for issue/PR pickers (#1352)

Replace local-only filtering in GitHub issue/PR picker dialogs with
server-side GitHub Search API queries. Search text is sent as a query
parameter to the server, which uses the GitHub Search API
(issuesAndPullRequests endpoint) with repo: qualifiers including fork
network support. Results are debounced at 350ms to respect API rate
limits.

- Add query parameter to GitHubAPI issuesList/prsList interface
- Server routes use Search API when query is present, standard list
  endpoint when absent
- Fork networks handled via repo:owner/repo OR repo:owner/upstream
- PR search fetches full PR details after Search API for head/base/draft
  fields
- Remove local filter memos from all three picker dialogs
- Add debounced search effect with abort controller cleanup
- Update VS Code backend and webview API for parity
- Update search placeholders in all locales

Closes #1350

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/i18n/messages/es.ts

@@ -1403,7 +1403,7 @@ export const dict: Record<I18nKey, string> = {
   "session.githubIssuePicker.title.createSession": "Nueva sesión desde issue de GitHub",
   "session.githubIssuePicker.description.select": "Selecciona un issue para vincularlo a esta sesión.",
   "session.githubIssuePicker.description.createSession": "Inicia una nueva sesión con contexto oculto del issue (título/cuerpo/etiquetas/comentarios).",
-  "session.githubIssuePicker.searchPlaceholder": "Buscar por título o #123, o pegar la URL del issue",
+  "session.githubIssuePicker.searchPlaceholder": "Buscar usando la sintaxis de búsqueda de código de GitHub",
   "session.githubIssuePicker.empty.noActiveProject": "No hay ningún proyecto activo seleccionado.",
   "session.githubIssuePicker.empty.runtimeUnavailable": "API de runtime de GitHub no disponible.",
   "session.githubIssuePicker.empty.notConnected": "GitHub no está conectado. Conecta tu cuenta de GitHub en configuración.",
@@ -1430,7 +1430,7 @@ export const dict: Record<I18nKey, string> = {
   "session.githubPrPicker.toast.loadDetailsFailed": "No se pudieron cargar los detalles de la PR",
   "session.githubPrPicker.title": "Vincular PR de GitHub",
   "session.githubPrPicker.description": "Selecciona una PR para adjuntar contexto de revisión a este mensaje.",
-  "session.githubPrPicker.searchPlaceholder": "Buscar por título o #123, o pegar la URL de la PR",
+  "session.githubPrPicker.searchPlaceholder": "Buscar usando la sintaxis de búsqueda de código de GitHub",
   "session.githubPrPicker.includeDiffAria": "Incluir diff de la PR en el contexto adjunto",
   "session.githubPrPicker.includeDiff": "Incluir diff de la PR",
   "session.githubPrPicker.empty.noActiveProject": "No hay ningún proyecto activo seleccionado.",
@@ -1497,8 +1497,8 @@ export const dict: Record<I18nKey, string> = {
   "session.githubIntegration.connect.title": "Conectar a GitHub",
   "session.githubIntegration.connect.description": "Vincula issues o PR para rellenar automáticamente los detalles del worktree",
   "session.githubIntegration.connect.action": "Conectar a GitHub",
-  "session.githubIntegration.search.issuesPlaceholder": "Buscar issues o introducir #123...",
-  "session.githubIntegration.search.prsPlaceholder": "Buscar PRs o introducir #456...",
+  "session.githubIntegration.search.issuesPlaceholder": "Buscar usando la sintaxis de búsqueda de código de GitHub",
+  "session.githubIntegration.search.prsPlaceholder": "Buscar usando la sintaxis de búsqueda de código de GitHub",
   "session.githubIntegration.empty.noIssuesFound": "No se encontraron issues",
   "session.githubIntegration.empty.noPullRequestsFound": "No se encontraron PR",
   "session.githubIntegration.actions.loadMore": "Cargar más",