test(02-01): add failing tests for athena model parser

- Cover standard provider/model strings for supported council members
- Validate edge case handling for model IDs with extra slashes
- Assert null output for malformed parser inputs

src/agents/athena/model-parser.test.ts

@@ -0,0 +1,73 @@
+import { describe, expect, test } from "bun:test"
+import { parseModelString } from "./model-parser"
+
+describe("parseModelString", () => {
+  describe("valid model strings", () => {
+    //#given provider/model strings with one separator
+    //#when parsing model strings
+    //#then it returns providerID and modelID parts
+
+    test("parses anthropic model", () => {
+      expect(parseModelString("anthropic/claude-opus-4-6")).toEqual({
+        providerID: "anthropic",
+        modelID: "claude-opus-4-6",
+      })
+    })
+
+    test("parses openai model", () => {
+      expect(parseModelString("openai/gpt-5.3-codex")).toEqual({
+        providerID: "openai",
+        modelID: "gpt-5.3-codex",
+      })
+    })
+
+    test("parses google model", () => {
+      expect(parseModelString("google/gemini-3-flash")).toEqual({
+        providerID: "google",
+        modelID: "gemini-3-flash",
+      })
+    })
+
+    test("parses xai model", () => {
+      expect(parseModelString("xai/grok-code-fast-1")).toEqual({
+        providerID: "xai",
+        modelID: "grok-code-fast-1",
+      })
+    })
+  })
+
+  describe("edge cases", () => {
+    //#given a model string with extra slashes
+    //#when parsing with first slash as separator
+    //#then provider is before first slash and model keeps remaining path
+
+    test("keeps extra slashes in model segment", () => {
+      expect(parseModelString("provider/model/with/extra/slashes")).toEqual({
+        providerID: "provider",
+        modelID: "model/with/extra/slashes",
+      })
+    })
+  })
+
+  describe("invalid model strings", () => {
+    //#given malformed or empty model strings
+    //#when parsing model strings
+    //#then it returns null
+
+    test("returns null for empty string", () => {
+      expect(parseModelString("")).toBeNull()
+    })
+
+    test("returns null for model without slash", () => {
+      expect(parseModelString("no-slash-model")).toBeNull()
+    })
+
+    test("returns null for empty provider", () => {
+      expect(parseModelString("/missing-provider")).toBeNull()
+    })
+
+    test("returns null for empty model", () => {
+      expect(parseModelString("missing-model/")).toBeNull()
+    })
+  })
+})