[dajiaohuang]

theme_selector() documents input_id as the Shiny input name, but its dropdown was always created with the literal ID theme. Passing a custom ID therefore left the label pointing at one ID while the actual input continued to emit the default ID.

Use input_id when constructing the dropdown and add a regression test for both the rendered input ID and its label association.

Validation:

• git diff --check passed.
• A task-local R 4.5.3 testthat::test_that script exercising the regression printed Test passed with 2 successes; the R process then exited abnormally with Windows code 1073741819. Full R CMD check was not run; this is not reported as a clean test-process pass.