Add per-model generation settings to the model selector

Each text and vision harness setting now carries the generation settings
its model takes (temperature, sampling limits, penalties, seed, reasoning
effort), edited in a modal under the model pick so the harness block stays
short. Nothing is set by default, so models keep their provider's own
values until a super admin or admin changes them.

A setting is only offered and only sent when the catalog says the model
takes it: OpenRouter's supported_parameters is now stored on
harness_models and refreshed by the hourly sync. Other providers list no
parameters, so their models get them all.

src/schemas/harness-schema.ts

@@ -45,6 +45,11 @@ export const SaveHarnessSettingsRequestSchema = z.object({
                 fallback: z.boolean(),
                 enabled: z.boolean(),
                 voice: z.string().trim().max(200).optional(),
+                /**
+                 * Generation settings (temperature, reasoning effort, ...).
+                 * Only the ones in `HarnessParameters` are kept.
+                 */
+                params: z.record(z.string(), z.union([z.number(), z.string()])).optional(),
             }),
         )
         .min(1, "Nothing to save")