Add Mistral as AI provider

- Add Mistral to KnownProvider type and model generation
- Implement Mistral-specific compat handling in openai-completions:
  - requiresToolResultName: tool results need name field
  - requiresAssistantAfterToolResult: synthetic assistant message between tool/user
  - requiresThinkingAsText: thinking blocks as <thinking> text
  - requiresMistralToolIds: tool IDs must be exactly 9 alphanumeric chars
- Add MISTRAL_API_KEY environment variable support
- Add Mistral tests across all test files
- Update documentation (README, CHANGELOG) for both ai and coding-agent packages
- Remove client IDs from gemini.md, reference upstream source instead

Closes #165

packages/ai/test/agent.test.ts

@@ -358,6 +358,20 @@ describe("Agent Calculator Tests", () => {
 			expect(result.toolCallCount).toBeGreaterThanOrEqual(1);
 		}, 30000);
 	});
+
+	describe.skipIf(!process.env.MISTRAL_API_KEY)("Mistral Provider Agent", () => {
+		const model = getModel("mistral", "devstral-medium-latest");
+
+		it("should calculate multiple expressions and sum the results", async () => {
+			const result = await calculateTest(model);
+			expect(result.toolCallCount).toBeGreaterThanOrEqual(2);
+		}, 30000);
+
+		it("should handle abort during tool execution", async () => {
+			const result = await abortTest(model);
+			expect(result.toolCallCount).toBeGreaterThanOrEqual(1);
+		}, 30000);
+	});
 });
 
 describe("agentLoopContinue", () => {