feat(combos): Cursor/Claude Default presets + bulk select/delete/strategy

- Add Cursor Default / Claude Default on Dashboard -> Combos to generate
  unprefixed combo names that match Cursor/Claude client model IDs,
  seeded with cu/... or cc/... so those clients can route through 9Router.
- Add multi-select bulk Delete and bulk Set strategy (Fallback / Round Robin / Fusion).
- Docs and unit tests for preset builder.

tests/unit/combo-presets.test.js

@@ -0,0 +1,102 @@
+import { describe, it, expect } from "vitest";
+import {
+  buildPresetItems,
+  buildCursorPresetItems,
+  buildClaudePresetItems,
+  isValidComboPresetName,
+} from "../../src/lib/comboPresets.js";
+
+describe("combo presets", () => {
+  it("rejects combo names with slashes or invalid chars", () => {
+    expect(isValidComboPresetName("composer-2.5")).toBe(true);
+    expect(isValidComboPresetName("claude-opus-5")).toBe(true);
+    expect(isValidComboPresetName("cu/composer-2.5")).toBe(false);
+    expect(isValidComboPresetName("bad name")).toBe(false);
+    expect(isValidComboPresetName("")).toBe(false);
+  });
+
+  it("Cursor live ids become unprefixed names seeded with cu/…", () => {
+    const items = buildCursorPresetItems({
+      liveModels: [
+        { id: "composer-2.5", name: "Composer 2.5" },
+        { id: "cursor-grok-4.6-high-fast", name: "Grok" },
+        { id: "bad/with-slash", name: "Invalid" },
+      ],
+    });
+
+    expect(items).toEqual([
+      { name: "composer-2.5", models: ["cu/composer-2.5"] },
+      { name: "cursor-grok-4.6-high-fast", models: ["cu/cursor-grok-4.6-high-fast"] },
+    ]);
+  });
+
+  it("Cursor falls back to static cu registry when live catalog is empty", () => {
+    const items = buildCursorPresetItems({ liveModels: [] });
+    expect(items.length).toBeGreaterThan(0);
+    expect(items.every((i) => i.models[0].startsWith("cu/"))).toBe(true);
+    expect(items.some((i) => i.name === "default")).toBe(true);
+    // No slash in combo name
+    expect(items.every((i) => !i.name.includes("/"))).toBe(true);
+  });
+
+  it("Claude aliases map opus → cc/claude-opus-5 and registry models seed cc/…", () => {
+    const items = buildClaudePresetItems();
+    const byName = Object.fromEntries(items.map((i) => [i.name, i]));
+
+    expect(byName["claude-opus-5"]).toEqual({
+      name: "claude-opus-5",
+      models: ["cc/claude-opus-5"],
+    });
+    expect(byName.opus).toEqual({
+      name: "opus",
+      models: ["cc/claude-opus-5"],
+    });
+    expect(byName.sonnet).toEqual({
+      name: "sonnet",
+      models: ["cc/claude-sonnet-5"],
+    });
+    expect(byName.haiku).toEqual({
+      name: "haiku",
+      models: ["cc/claude-haiku-4-5-20251001"],
+    });
+    expect(byName.fable).toEqual({
+      name: "fable",
+      models: ["cc/claude-fable-5"],
+    });
+    expect(byName.default).toEqual({
+      name: "default",
+      models: ["cc/claude-sonnet-5"],
+    });
+    expect(byName.opusplan).toEqual({
+      name: "opusplan",
+      models: ["cc/claude-opus-5"],
+    });
+  });
+
+  it("marks existing names with exists: true", () => {
+    const items = buildPresetItems("cursor", {
+      liveModels: [
+        { id: "composer-2.5" },
+        { id: "gpt-5.3-codex" },
+      ],
+      existingNames: ["composer-2.5"],
+    });
+
+    expect(items).toEqual([
+      { name: "composer-2.5", models: ["cu/composer-2.5"], exists: true },
+      { name: "gpt-5.3-codex", models: ["cu/gpt-5.3-codex"], exists: false },
+    ]);
+  });
+
+  it("returns empty for unknown source", () => {
+    expect(buildPresetItems("unknown")).toEqual([]);
+  });
+
+  it("drops invalid names from Claude/Cursor catalogs", () => {
+    const cursor = buildPresetItems("cursor", {
+      liveModels: [{ id: "ok-model" }, { id: "no/slash" }, { id: "has space" }],
+      existingNames: [],
+    });
+    expect(cursor.map((i) => i.name)).toEqual(["ok-model"]);
+  });
+});