[P2][Tier 4] Enable agents to find screenshots and attach them to filed issues

Tier 4 — FC-specific leverage · Priority: P2 · depends on #3329

Gap

When an agent files a bug (see #3329), it can't easily include visual evidence. There's no documented way for an agent to locate screenshots (e.g., from integration/UI test runs, diagnostics captures, or a known output location) and attach them to an issue, so agent-filed bugs are text-only even when a screenshot would make the problem obvious.

Investment

• Document (and, where needed, build a small tool/skill) a path for agents to:
  • Find relevant screenshots — identify where they're produced (integration/UI test artifacts, .vscode-test output, diagnostics/log collection, UI-automation captures) and how to locate the most recent/relevant ones.
  • Attach them to an issue in microsoft/vscode-dotnettools — a working, documented method (e.g., GitHub asset upload / gh + API) so the image renders in the issue body or a comment.
• Fold the attach step into the bug-filing flow from #3329 so a filed bug can carry screenshots.

Acceptance criteria

• Documented location(s)/command(s) where agents can find screenshots.
• A documented, working method for an agent to attach a screenshot to a microsoft/vscode-dotnettools issue.

Part of epic #3273 · depends on #3329

Start by tracing the bug-filing flow from #3329 and identifying where integration/UI test artifacts, .vscode-test output, diagnostics captures, or UI-automation screenshots are produced. Document how to locate the relevant image and use GitHub asset upload or gh plus the API to attach it to a microsoft/vscode-dotnettools issue. Done means both screenshot discovery and attachment are documented and incorporated into the filing flow.