Fix: omit untitled session in sessions list

[chrmarti]

#321269

[Copilot]

Pull request overview

Adjusts the agent-host session listing overlay logic so that “provisional” (not-yet-materialized) sessions don’t leak into the sessions list while still idle, addressing the “untitled session shows up” scenario described by the PR title. It also adds targeted regression coverage and introduces CI “stability” reruns for the Agents Window smoke tests.

Changes:

• Refines the listSessions() overlay source to exclude idle provisional sessions from the overlayed session summaries.
• Adds a regression test for provisional-session visibility behavior during an active turn.
• Adds CI steps that rerun the Agents Window smoke tests 20× on multiple platforms.

Show a summary per file

File	Description
src/vs/platform/agentHost/test/node/agentService.test.ts	Updates overlay-summary accessor usage and adds a new regression test for provisional session listing.
src/vs/platform/agentHost/node/agentService.ts	Switches overlay logic to use the new filtered overlay-summary accessor and documents the rationale.
src/vs/platform/agentHost/node/agentHostStateManager.ts	Replaces the “all summaries” accessor with a filtered overlay accessor intended to suppress idle provisional sessions.
build/azure-pipelines/win32/steps/product-build-win32-test.yml	Adds a “run Agents Window smoke tests 20×” stability step (Windows).
build/azure-pipelines/linux/steps/product-build-linux-test.yml	Adds a “run Agents Window smoke tests 20×” stability step (Linux).
build/azure-pipelines/darwin/steps/product-build-darwin-test.yml	Adds a “run Agents Window smoke tests 20×” stability step (macOS).
.github/workflows/pr-win32-test.yml	Adds a “run Agents Window smoke tests 20×” stability step (Windows PR workflow).
.github/workflows/pr-linux-test.yml	Adds a “run Agents Window smoke tests 20×” stability step (Linux PR workflow).

Copilot's findings

• Files reviewed: 8/8 changed files
• Comments generated: 7