feat(chat,app): Model view in sidebar + split key/model selectors

- move the model picker out of the chat header into a dedicated "Model" sidebar
  view; sidebar now seeds two default panels (Model on top, Extensions below)
- split the single model dropdown into two stacked selects: a key selector
  (distinct credential keys) + a model selector (models under the current key)
- pure model-select helpers (splitModelName/joinModelName/modelKeys/modelsForKey),
  split on the FIRST slash so multi-slash model names stay intact
- onSelect still emits the full `<key>/<model>` string (ChatRequest.model unchanged)

1 files changed, 58 insertions, 0 deletions

diff --git a/src/features/chat/model-select.test.ts b/src/features/chat/model-select.test.ts
new file mode 100644
index 0000000..109cae1
--- /dev/null
+++ b/src/features/chat/model-select.test.ts
@@ -0,0 +1,58 @@
+import { describe, expect, it } from "vitest";
+import { joinModelName, modelKeys, modelsForKey, splitModelName } from "./model-select";
+
+describe("splitModelName", () => {
+	it("splits on the first slash", () => {
+		expect(splitModelName("openai/gpt-4")).toEqual({ key: "openai", model: "gpt-4" });
+	});
+
+	it("keeps slashes in the model part (splits only the first)", () => {
+		expect(splitModelName("openrouter/anthropic/claude")).toEqual({
+			key: "openrouter",
+			model: "anthropic/claude",
+		});
+	});
+
+	it("treats a slashless name as all key", () => {
+		expect(splitModelName("local")).toEqual({ key: "local", model: "" });
+	});
+});
+
+describe("joinModelName", () => {
+	it("recombines key + model", () => {
+		expect(joinModelName("openai", "gpt-4")).toBe("openai/gpt-4");
+	});
+
+	it("returns just the key when the model is empty", () => {
+		expect(joinModelName("local", "")).toBe("local");
+	});
+
+	it("round-trips with splitModelName", () => {
+		const full = "openrouter/anthropic/claude";
+		const { key, model } = splitModelName(full);
+		expect(joinModelName(key, model)).toBe(full);
+	});
+});
+
+describe("modelKeys", () => {
+	it("returns distinct keys in first-seen order", () => {
+		expect(
+			modelKeys(["openai/gpt-4", "openai/gpt-4o", "anthropic/claude-3", "google/gemini"]),
+		).toEqual(["openai", "anthropic", "google"]);
+	});
+
+	it("is empty for no models", () => {
+		expect(modelKeys([])).toEqual([]);
+	});
+});
+
+describe("modelsForKey", () => {
+	it("returns the model suffixes under a key, in order", () => {
+		const models = ["openai/gpt-4", "anthropic/claude-3", "openai/gpt-4o"];
+		expect(modelsForKey(models, "openai")).toEqual(["gpt-4", "gpt-4o"]);
+	});
+
+	it("returns empty for an unknown key", () => {
+		expect(modelsForKey(["openai/gpt-4"], "anthropic")).toEqual([]);
+	});
+});