docs(config): explain Mistral Vibe key setup [skip ci]

Point the existing Mistral provider at current Vibe Code key guidance and document setup, shared allowance and billing boundaries. Live use in Codewhale remains unverified.

Verified: existing Mistral provider metadata test 1/1 on Mac, provider-registry and example-config checks, and captured Mac CLI build. No live provider call was made.

config.example.toml

@@ -898,6 +898,7 @@ base_url = "https://api.deepseek.com/beta"
 # OpenAI-compatible Chat Completions route.
 # Provider aliases: mistral, mistral-ai, mistralai, la-plateforme
 # Env var aliases: MISTRAL_API_KEY, MISTRAL_BASE_URL, MISTRAL_MODEL
+# Vibe Code subscription setup: docs/MISTRAL_VIBE.md
 [providers.mistral]
 # api_key = "YOUR_MISTRAL_API_KEY"
 # base_url = "https://api.mistral.ai/v1"

crates/config/assets/provider_descriptors.json

@@ -1567,9 +1567,9 @@
       "wire_policy": "chat_completions",
       "credential_help": {
         "acquisition": "api_key",
-        "credential_url": "https://console.mistral.ai/api-keys",
-        "docs_url": "https://docs.mistral.ai/",
-        "guidance": "Create a Mistral API key in the Mistral Console (la Plateforme)."
+        "credential_url": "https://chat.mistral.ai/code/extensions",
+        "docs_url": "https://docs.mistral.ai/vibe/code/cli/api-keys-profiles",
+        "guidance": "Use a Vibe Code API key or a Mistral Studio API key. Plan allowances and pay-as-you-go depend on your organization."
       },
       "selectable": true,
       "retired": false,

crates/config/src/tests.rs

@@ -5144,7 +5144,7 @@ fn mistral_provider_resolves_defaults_and_metadata() {
     );
     assert_eq!(
         help.credential_url,
-        Some("https://console.mistral.ai/api-keys")
+        Some("https://chat.mistral.ai/code/extensions")
     );
 
     let config: ConfigToml = toml::from_str(

docs/MISTRAL_VIBE.md

@@ -0,0 +1,28 @@
+# Mistral Vibe Code
+
+Codewhale's `mistral` provider can be configured with a Vibe Code API key. An
+actual Codewhale conversation using that key has not yet been verified. You do
+not need a separate provider or a Vibe process to configure the key.
+
+1. In [Mistral Code > Vibe CLI](https://chat.mistral.ai/code/extensions),
+   create a Vibe Code API key. Mistral documents this key for Free mode, paid
+   plans and pay-as-you-go. Keep the key out of prompts and shell history.
+2. Run `codewhale auth set --provider mistral` and enter the key when prompted,
+   or choose Mistral in `/provider` and enter it there. Alternatively, provide
+   it to the process through `MISTRAL_API_KEY`. A saved Codewhale credential
+   takes precedence over the environment variable; an explicit `--api-key`
+   takes precedence for that launch.
+3. Start `codewhale --provider mistral --model mistral-medium-latest`, or select
+   Mistral and the model in the provider and model pickers. Mistral recommends
+   `mistral-medium-latest` for reasoning and code. Model access depends on the
+   account and plan. The default API base is `https://api.mistral.ai/v1`.
+
+Mistral says included monthly usage is shared across Studio, the API and Vibe
+Code. When it runs out, requests may stop or use prepaid pay-as-you-go credits,
+depending on the organization's settings. Check the [subscription
+settings](https://admin.mistral.ai/subscription) before use. Codewhale's
+token-price estimates are not an invoice, remaining allowance or proof of a
+subscription charge. Mistral's [key and billing
+guide](https://docs.mistral.ai/vibe/code/cli/api-keys-profiles) has current
+details. Codewhale does not automatically import Vibe's keyring or sign in
+through Vibe's browser flow.