Rename `autocomplete_replace_underscores` to `autocomplete_keep_underscores`
(default false) so both autocomplete toggles read as "keep" semantics.
`insertTag` now honors the setting for both tag and artist modes, matching
the dropdown display. Embedding insertion always preserves underscores
because the names are filesystem identifiers.
- ui_definitions: rename option, flip default, update label
- scripts/autocomplete: rename handler, checkbox, and config-bridge keys
- javascript/autocomplete: invert render polarity; insertTag takes a `kind`
parameter; drop the artist-mode hardcoded underscore replacement so the
setting controls tags and artists uniformly
Closes#4827
- new autocomplete_translations setting (default off); checkbox in script accordion + locale hint
- get_cached gates companion load on the opt; toggle-flip auto-syncs missing files in a background thread
- list_all_sync, local_names and config_json filter out *.translations.json so companion files never surface as selectable dicts
- one-time per-name warning when opt is on but companion is missing locally
- create scripts/autocomplete.py as always-on script with dictionary
management UI (dropdown, refresh, update, settings controls)
- move autocomplete settings from Settings > Extra Networks to hidden
options, controlled via script UI with JS config bridge
- remove early exit in autocomplete.js when no dictionaries enabled,
allowing dictionaries enabled via script UI to work without reload
- add id-based suffix matching to setHints.js for unique button hints
- add locale_en.json entries with tooltips for all autocomplete controls