FEATURE: Unavailable state for semantic search when sort is not Relevant

[markvanlan]

This PR adds an "unavailable" state for the AI semantic search toggle. Currently the AI toggle disappears when the sort by is anything but Relevance which makes the UI confusing for users looking for AI results. This should help!

Note there are no specs for this feature. I'm not sure what the LLM extraction mentioned here is, so I didn't touch it.

discourse-ai/spec/system/embeddings/semantic_search_spec.rb

Lines 42 to 48 in 534b0df

	skip "TODO: Implement test after doing LLM abstraction" do
	it "performs AI search in the background and hides results by default" do
	visit("/search?expanded=true")
	search_page.type_in_search("apple pie")
	search_page.click_search_button
	end
	end

No UI change for regular ol' searching

But when a different sort order is selected, we now have an unavailable state with a tooltip explaining

[keegangeorge]

Thanks @markvanlan, this looks good! Just a few small comments to address.

About the system spec, yes please feel free to leave as is, I will create a separate todo and follow-up with relevant tests.

I also noticed this PR introduces in a small bug with the text label.

To repro:

1. Go from quick search to advanced search
2. Search for “test”
3. Toggle AI
4. Append “themes” to search to be “test themes”
5. Enter to search
   [The text label says: "Press 'search' to begin looking for new results with AI" while AI results are being fetched, and is replaced by "Hiding %{count} results found using AI"]

This should instead be:
["Searching for more results using AI" while AI results are being fetched and then as it is now, replaced by "Hiding %{count} results found using AI"].

[keegangeorge]

Awesome! 👏🏽