Run models on sensible generation defaults out of the box

A fresh install had no generation settings until someone set one, so every
model ran on whatever its provider happened to use. Each harness now has a
default (text 0.3 temperature, vision 0.2, image the provider's own), shown
in the model settings modal so what a model runs on is never a guess.

The defaults are only sent to a model whose catalog lists the field, so a
provider that says nothing about its models still gets no parameter it
might reject; anything saved on a harness or bot wins over the default.

src/harness/text/grab-chat-params.ts

@@ -1,5 +1,7 @@
 import {
     HarnessParameters,
+    harnessParameterValue,
+    modelAdvertisesParameter,
     modelTakesParameter,
 } from "@/src/dict/harness-parameter-dict";
 import grabHarnessSetting from "@/src/functions/backend/db/harness/grab-harness-setting";
@@ -13,10 +15,10 @@ type Params = {
 
 /**
  * A model's generation settings for one call: what is saved in the
- * harness's setting (the workspace's, the bot's, else the default),
- * keyed by the field sent on the wire, keeping only what the model says it
- * takes. Empty when none are set, so the model gets its provider's
- * defaults.
+ * harness's setting (the workspace's, the bot's, else the default), else
+ * `HarnessParameterDefaults` so a fresh install is ready to go. Keyed by
+ * the field sent on the wire, keeping only what the model says it takes
+ * (a default only where the model explicitly advertises it).
  */
 export default async function grabChatParams({
     harness,
@@ -34,7 +36,11 @@ export default async function grabChatParams({
     return (model) =>
         Object.fromEntries(
             HarnessParameters.flatMap((parameter) => {
-                const value = setting.options[parameter.key];
+                const { value, saved } = harnessParameterValue({
+                    harness,
+                    params: setting.options,
+                    key: parameter.key,
+                });
 
                 if (typeof value != "number" && typeof value != "string") return [];
                 if (!value && value !== 0) return [];
@@ -45,6 +51,14 @@ export default async function grabChatParams({
                     })
                 )
                     return [];
+                if (
+                    !saved &&
+                    !modelAdvertisesParameter({
+                        parameter,
+                        supported: model.supported_parameters,
+                    })
+                )
+                    return [];
 
                 const key = "wire" in parameter ? parameter.wire : parameter.key;