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

package-lock.json

@@ -983,6 +983,24 @@
 			"resolved": "packages/web-ui",
 			"link": true
 		},
+		"node_modules/@mistralai/mistralai": {
+			"version": "1.10.0",
+			"resolved": "https://registry.npmjs.org/@mistralai/mistralai/-/mistralai-1.10.0.tgz",
+			"integrity": "sha512-tdIgWs4Le8vpvPiUEWne6tK0qbVc+jMenujnvTqOjogrJUsCSQhus0tHTU1avDDh5//Rq2dFgP9mWRAdIEoBqg==",
+			"dependencies": {
+				"zod": "^3.20.0",
+				"zod-to-json-schema": "^3.24.1"
+			}
+		},
+		"node_modules/@mistralai/mistralai/node_modules/zod": {
+			"version": "3.25.76",
+			"resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
+			"integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+			"license": "MIT",
+			"funding": {
+				"url": "https://github.com/sponsors/colinhacks"
+			}
+		},
 		"node_modules/@napi-rs/canvas": {
 			"version": "0.1.84",
 			"resolved": "https://registry.npmjs.org/@napi-rs/canvas/-/canvas-0.1.84.tgz",
@@ -6559,6 +6577,7 @@
 			"dependencies": {
 				"@anthropic-ai/sdk": "0.71.2",
 				"@google/genai": "1.31.0",
+				"@mistralai/mistralai": "1.10.0",
 				"@sinclair/typebox": "^0.34.41",
 				"ajv": "^8.17.1",
 				"ajv-formats": "^3.0.1",