Add live AI checks to system health (#3155)

* Add live AI checks to system health

Give super admins a dedicated AI status view with bounded liveness probes for LLMs, vector stores, pgvector, and embedding endpoints. Record sanitized failures in both the system debug log and Rails logger, and document the recommended local configuration.\n\nCloses #3145

* Fix AI health CI checks

* Address AI health review feedback

* Correct Ollama model preload guidance

* Distinguish OpenAI-compatible providers

* Make Ollama startup readiness explicit

* Recognize Cloudflare AI endpoints

test/models/vector_store_test.rb

@@ -0,0 +1,34 @@
+require "test_helper"
+
+class VectorStoreTest < ActiveSupport::TestCase
+  EMBEDDING_ENVIRONMENT = %w[
+    EMBEDDING_MODEL EMBEDDING_DIMENSIONS EMBEDDING_URI_BASE
+    EMBEDDING_ACCESS_TOKEN OPENAI_URI_BASE OPENAI_ACCESS_TOKEN
+  ].index_with(nil).freeze
+
+  test "embedding defaults use a matching model and vector width" do
+    ClimateControl.modify(EMBEDDING_ENVIRONMENT) do
+      assert_equal "mxbai-embed-large", VectorStore.embedding_model
+      assert_equal 1024, VectorStore.embedding_dimensions
+    end
+  end
+
+  test "embedding credentials match runtime environment precedence" do
+    ClimateControl.modify(EMBEDDING_ENVIRONMENT.merge(
+      "EMBEDDING_ACCESS_TOKEN" => "embedding-token",
+      "OPENAI_ACCESS_TOKEN" => "openai-token"
+    )) do
+      assert_equal "embedding-token", VectorStore.embedding_access_token
+    end
+
+    ClimateControl.modify(EMBEDDING_ENVIRONMENT.merge(
+      "OPENAI_ACCESS_TOKEN" => "openai-token"
+    )) do
+      assert_equal "openai-token", VectorStore.embedding_access_token
+    end
+
+    ClimateControl.modify(EMBEDDING_ENVIRONMENT) do
+      assert_nil VectorStore.embedding_access_token
+    end
+  end
+end