Server becomes the source of truth for sampling parameter defaults (#20558)

* webui: make server the source of truth for sampling defaults

* webui: fix Custom badge for sampling parameters

* webui: log user overrides after server sync

* chore: update webui build output

* fix: Default values for sampling settings config object

* chore: update webui build output

---------

Co-authored-by: Aleksander Grygier <aleksander.grygier@gmail.com>

tools/server/webui/src/lib/constants/settings-config.ts

@@ -1,8 +1,8 @@
 import { ColorMode } from '$lib/enums/ui';
 import { Monitor, Moon, Sun } from '@lucide/svelte';
 
-export const SETTING_CONFIG_DEFAULT: Record<string, string | number | boolean> = {
-	// Note: in order not to introduce breaking changes, please keep the same data type (number, string, etc) if you want to change the default value. Do not use null or undefined for default value.
+export const SETTING_CONFIG_DEFAULT: Record<string, string | number | boolean | undefined> = {
+	// Note: in order not to introduce breaking changes, please keep the same data type (number, string, etc) if you want to change the default value.
 	// Do not use nested objects, keep it single level. Prefix the key if you need to group them.
 	apiKey: '',
 	systemMessage: '',
@@ -30,27 +30,30 @@ export const SETTING_CONFIG_DEFAULT: Record<string, string | number | boolean> =
 	agenticMaxToolPreviewLines: 25,
 	showToolCallInProgress: false,
 	alwaysShowAgenticTurns: false,
-	// make sure these default values are in sync with `common.h`
-	samplers: 'top_k;typ_p;top_p;min_p;temperature',
+	// sampling params: empty means "use server default"
+	// the server / preset is the source of truth
+	// empty values are shown as placeholders from /props in the UI
+	// and are NOT sent in API requests, letting the server decide
+	samplers: '',
 	backend_sampling: false,
-	temperature: 0.8,
-	dynatemp_range: 0.0,
-	dynatemp_exponent: 1.0,
-	top_k: 40,
-	top_p: 0.95,
-	min_p: 0.05,
-	xtc_probability: 0.0,
-	xtc_threshold: 0.1,
-	typ_p: 1.0,
-	repeat_last_n: 64,
-	repeat_penalty: 1.0,
-	presence_penalty: 0.0,
-	frequency_penalty: 0.0,
-	dry_multiplier: 0.0,
-	dry_base: 1.75,
-	dry_allowed_length: 2,
-	dry_penalty_last_n: -1,
-	max_tokens: -1,
+	temperature: undefined,
+	dynatemp_range: undefined,
+	dynatemp_exponent: undefined,
+	top_k: undefined,
+	top_p: undefined,
+	min_p: undefined,
+	xtc_probability: undefined,
+	xtc_threshold: undefined,
+	typ_p: undefined,
+	repeat_last_n: undefined,
+	repeat_penalty: undefined,
+	presence_penalty: undefined,
+	frequency_penalty: undefined,
+	dry_multiplier: undefined,
+	dry_base: undefined,
+	dry_allowed_length: undefined,
+	dry_penalty_last_n: undefined,
+	max_tokens: undefined,
 	custom: '', // custom json-stringified object
 	// experimental features
 	pyInterpreterEnabled: false,