Confirming an inline rename after deleting the entire symbol name or
entering only whitespace currently submits an invalid rename request to
the language server. This can remove the symbol text instead of leaving
the source unchanged.

Treat empty and whitespace-only replacements as successful no-ops after
dismissing the inline rename UI. Returning a completed task also
consumes the confirmation action, preventing Enter from propagating back
into the editor. Non-blank rename behavior remains unchanged.

The regression test covers both empty and whitespace-only rename fields,
verifying that no LSP rename request is sent and the original buffer
remains intact.

Release Notes:

- editor: Fixed confirming a blank symbol LSP-rename modifying the
source code