Add a nested field-level allowlist under [server] so listeners can be managed remotely without exposing server.api auth_header or other bind-identity fields.
The save and patch paths under test are async, so the tests now use tokio::fs instead of blocking std::fs. The config_store tests also switch to tempfile::tempdir() for panic-safe cleanup instead of manual remove_dir_all.
render_top_level_section serialized a section in isolation, so nested sub-tables ([general.links], [general.modes]) were emitted as bare [links]/[modes] top-level headers and duplicated on load. Serialize the section inside a wrapper keyed by its name to keep dotted headers.
find_toml_table_bounds only spanned the first contiguous block, leaving scattered sub-tables behind as duplicates on repeated saves. Replace it with find_all_table_blocks and drop every block belonging to the section during upsert.
show_link is a legacy top-level scalar/array, not a [table]; the upsert machinery appended a bare key at EOF (landing inside the previous table) and duplicated it on repeat. Remove it from EDITABLE_SECTIONS; the editable general.links.show sub-table covers the case.
Add tests for dotted sub-tables, idempotent saves, non-contiguous layouts, show_link rejection, and integer/float/string coercion of public_port.
Alexey