ui: model status and load progress via /models/sse feed (#24878)

* ui: model status and load progress via /models/sse feed

* ui: centralize SSE wire-format delimiters into shared constants for the chat and /models/sse parsers

* ui: type /models/sse event names as a ServerModelsSseEventType enum

Address review from allozaur

tools/ui/src/lib/constants/api-endpoints.ts

@@ -1,7 +1,8 @@
 export const API_MODELS = {
 	LIST: '/v1/models',
 	LOAD: '/models/load',
-	UNLOAD: '/models/unload'
+	UNLOAD: '/models/unload',
+	SSE: '/models/sse'
 };
 
 // chat completion routes, the control route drives realtime inference (e.g. end reasoning)

tools/ui/src/lib/constants/index.ts

@@ -37,6 +37,8 @@ export * from './mcp-form';
 export * from './mcp-resource';
 export * from './message-export';
 export * from './model-id';
+export * from './model-loading';
+export * from './sse';
 export * from './precision';
 export * from './processing-info';
 export * from './pwa';

tools/ui/src/lib/constants/model-loading.ts

@@ -0,0 +1,14 @@
+/**
+ * Labels shown while a model loads, keyed by the stage reported on /models/sse.
+ */
+export const MODEL_LOAD_STAGE_LABELS: Record<ApiModelLoadStage, string> = {
+	text_model: 'Loading weights',
+	spec_model: 'Loading draft',
+	mmproj_model: 'Loading projector'
+};
+
+/**
+ * Share of the bar reserved for each load phase after text_model.
+ * text_model fills the rest, so a plain model reaches 100% on its own.
+ */
+export const MODEL_LOAD_TAIL_SHARE = 0.1;

tools/ui/src/lib/constants/sse.ts

@@ -0,0 +1,16 @@
+/**
+ * Server-sent events wire format, shared by the chat stream and the
+ * /models/sse status feed (text/event-stream).
+ */
+
+// blank line between two events
+export const SSE_RECORD_SEPARATOR = '\n\n';
+
+// line break inside an event
+export const SSE_LINE_SEPARATOR = '\n';
+
+// data field prefix, the value follows after an optional space
+export const SSE_DATA_PREFIX = 'data:';
+
+// end-of-stream marker on the chat completion stream
+export const SSE_DONE_MARKER = '[DONE]';