Webui/prompt processing progress (#18300)

* webui: display prompt preprocessing progress

* webui: add percentage/ETA and exclude cached tokens from progress

Address review feedback from ngxson

* webui: add minutes and first chunk (0%) case

* Update tools/server/webui/src/lib/components/app/chat/ChatMessages/ChatMessageAssistant.svelte

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

* Update tools/server/webui/src/lib/components/app/chat/ChatMessages/ChatMessageAssistant.svelte

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

* webui: address review feedback from allozaur

* chore: update webui build output

* webui: address review feedback from allozaur

* nit

* chore: update webui build output

* feat: Enhance chat processing state

* feat: Improve chat processing statistics UI

* chore: update webui build output

* feat: Add live generation statistics to processing state hook

* feat: Persist prompt processing stats in hook for better UX

* refactor: Enhance ChatMessageStatistics for live stream display

* feat: Implement enhanced live chat statistics into assistant message

* chore: update webui build output

* fix: Proper tab for each stage of prompt processing/generation

* chore: update webui build output

* fix: Improved ETA calculation & display logic

* chore: update webui build output

* feat: Simplify logic & remove ETA from prompt progress

* chore: update webui build output

---------

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

tools/server/webui/src/lib/stores/chat.svelte.ts

@@ -324,6 +324,7 @@ class ChatStore {
 			topP: currentConfig.top_p ?? 0.95,
 			speculative: false,
 			progressPercent,
+			promptProgress,
 			promptTokens,
 			promptMs,
 			cacheTokens
@@ -534,7 +535,7 @@ class ChatStore {
 					conversationsStore.updateMessageAtIndex(idx, { toolCalls: streamedToolCallContent });
 				},
 				onModel: (modelName: string) => recordModel(modelName),
-				onTimings: (timings: ChatMessageTimings, promptProgress?: ChatMessagePromptProgress) => {
+				onTimings: (timings?: ChatMessageTimings, promptProgress?: ChatMessagePromptProgress) => {
 					const tokensPerSecond =
 						timings?.predicted_ms && timings?.predicted_n
 							? (timings.predicted_n / timings.predicted_ms) * 1000
@@ -1032,7 +1033,7 @@ class ChatStore {
 						});
 					},
 
-					onTimings: (timings: ChatMessageTimings, promptProgress?: ChatMessagePromptProgress) => {
+					onTimings: (timings?: ChatMessageTimings, promptProgress?: ChatMessagePromptProgress) => {
 						const tokensPerSecond =
 							timings?.predicted_ms && timings?.predicted_n
 								? (timings.predicted_n / timings.predicted_ms) * 1000