webui: fix tool selector toggle/counter, key tools by stable identity (#24065)
* webui: fix tool selector toggle/counter, key tools by stable identity
Key the disabled set, counts and toggles by a stable per-tool key
instead of bare function name, deduped from one canonical list. Per-tool
checkboxes become presentational (single row handler, no nested button),
category checkboxes drop the tristate (n/total carries partial). One
getEnabledToolsForLLM keeps normalized MCP schemas and dedupes by name.
* ui: use SvelteSet and SvelteMap for local tool collections to satisfy svelte/prefer-svelte-reactivity