Show deprecated APIs in code completion and hover information

Objo Studio already reports deprecated API usage after code is compiled, but code completion and symbol hover do not identify deprecated items while developers are discovering or inspecting an API.

Show deprecated APIs consistently in completion and hover information. Deprecated entries remain searchable and insertable for compatibility, but completion renders them with a strikethrough, presents replacement guidance, ranks them below non-deprecated alternatives, and avoids choosing them for ghost-text suggestions when a current alternative exists. Hover information prominently displays the deprecation message while retaining the normal signature and documentation.

The feature applies generically to built-in and user-defined deprecated APIs rather than special-casing individual standard-library members.