In strings, the following are not highlighted:

1. Escape sequences like \n, \t, \\ are shown in the same color as regular string text escape sequences not highlighted in strings #2552
2. In f-strings like f"""{keyname}""", the {keyname} expression is in the same color as regular string text

Expected: Escape sequences should have distinct coloring, and identifiers inside f-string braces should receive semantic token classification.