I'm aware of the 25.4 issue where VS Code looses the database connection after compiling a pl/sql package in a file - and have downgraded to previous release 25.3.2. – but am seeing similar behaviour after have co-pilot edit the code in a file. The compilation buttons also disappear. File type still shows as PL/SQL in the bottom menu.
Seems that it you change the filetype from PLSQL to something else (C++, as an example) then change it back to PLSQL again - then the compile buttons reappear and all is good.
Not sure if this is related to the 25.4 compiler issue so highlighting in case..