Add prompt_id support to progress_text WS messages (#9002)

## Summary

Add frontend support for `prompt_id` in `progress_text` binary WS
messages, enabling parallel workflow execution to route progress text to
the correct active prompt.

Backend PR: https://github.com/Comfy-Org/ComfyUI/pull/12540

## Changes

- Advertise `supports_progress_text_metadata` in client feature flags
- Decode `prompt_id` from new binary format when flag is active
- Add optional `prompt_id` to `zProgressTextWsMessage` schema
- Filter `progress_text` events by `activePromptId` — skip messages for
non-active prompts

## Deployment

Can be deployed independently in any order — feature flag negotiation
ensures graceful degradation.

Part of COM-12671

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9002-Add-prompt_id-support-to-progress_text-WS-messages-30d6d73d365081acabbcdac939e0c751)
by [Unito](https://www.unito.io)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Progress text updates can include optional metadata so richer context
is available.
* **Bug Fixes / Improvements**
* Progress updates are now filtered to show only the currently active
prompt, reducing cross-talk from concurrent operations and improving
update accuracy.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: GitHub Action <action@github.com>

src/scripts/api.ts

@@ -623,15 +623,44 @@ export class ComfyApi extends EventTarget {
 
           let imageMime
           switch (eventType) {
-            case 3:
-              const decoder = new TextDecoder()
-              const data = event.data.slice(4)
-              const nodeIdLength = view.getUint32(4)
-              this.dispatchCustomEvent('progress_text', {
-                nodeId: decoder.decode(data.slice(4, 4 + nodeIdLength)),
-                text: decoder.decode(data.slice(4 + nodeIdLength))
-              })
+            case 3: {
+              try {
+                const decoder3 = new TextDecoder()
+                const rawData = event.data.slice(4)
+                const rawView = new DataView(rawData)
+
+                let offset = 0
+                let promptId: string | undefined
+
+                if (
+                  this.getClientFeatureFlags()?.supports_progress_text_metadata
+                ) {
+                  const promptIdLength = rawView.getUint32(offset)
+                  offset += 4
+                  promptId = decoder3.decode(
+                    rawData.slice(offset, offset + promptIdLength)
+                  )
+                  offset += promptIdLength
+                }
+
+                const nodeIdLength = rawView.getUint32(offset)
+                offset += 4
+                const nodeId = decoder3.decode(
+                  rawData.slice(offset, offset + nodeIdLength)
+                )
+                offset += nodeIdLength
+                const text = decoder3.decode(rawData.slice(offset))
+
+                this.dispatchCustomEvent('progress_text', {
+                  nodeId,
+                  text,
+                  ...(promptId !== undefined && { prompt_id: promptId })
+                })
+              } catch (e) {
+                console.warn('Failed to parse progress_text binary message', e)
+              }
               break
+            }
             case 1:
               const imageType = view.getUint32(4)
               const imageData = event.data.slice(8)