Cache chat progress content part

[pwang347]

Metric (Renderer)	Insiders (without fix)	Code OSS (with fix)
Trace duration	~55s	~23s
Heap baseline	171 MB	112 MB
Heap peak	183 MB	117 MB
MajorGC count	55	2
MajorGC rate	1.0/s	0.09/s
MajorGC total time	19,418 ms	650 ms
MajorGC % of wall time	35%	3%
MajorGC avg duration	353 ms	325 ms
Avg freed per MajorGC	~6-8 MB	~1.8 MB
MinorGC count	10	24
Incremental marking events	33,927	1,130

[Copilot]

Pull request overview

This PR aims to reduce re-creation of chat tool progress UI parts by caching and updating an existing ChatProgressContentPart instance during tool streaming/progress updates in the chat widget.

Changes:

• Cache a ChatProgressContentPart in the tool streaming subpart and update it via updateMessage(...) instead of recreating it.
• Cache a ChatProgressContentPart in the tool progress subpart and update it via updateMessage(...) instead of recreating it.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatToolStreamingSubPart.ts	Reuses a single progress content part while tool invocation is in streaming state, updating message content in place.
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatToolProgressPart.ts	Reuses a single progress content part for tool progress rendering, updating message content in place.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 2

[github-actions]

Screenshot Changes

Base: 1028f069 Current: c70ed7a8

Changed (2)

agentSessionsViewer/WithBadge/Dark

Before	After

agentSessionsViewer/WithBadge/Light

Before	After