Add VS Code malicious-workspace audit notes, fixtures, and repro plan

[kajf]

Motivation

• Capture a source-level audit of VS Code attack surfaces related to opening attacker-controlled repositories and prepare benign fixtures for runtime validation.
• Enumerate and prioritize risky code paths (tasks, debug, terminal links, markdown/webviews, MCP, Git local-config) and document next focused experiments for reproducible verification.

Description

• Add a new audits/vscode-msrc-oss-bounty/ audit collection with multiple audit passes and triage notes, including source-audit, deep-audit, git-local-config-audit, mcp-trust-audit, builtin-task-provider-audit, terminal-opener-audit, markdown-preview-audit, ranked-code-paths.md, repro-plan.md, sources.md, and other supporting notes.
• Add a suite of benign, marker-based fixtures under fixtures/vscode-malicious-workspace/ to exercise scenarios: automatic/manual tasks, built-in provider autodetect (npm/gulp), terminal link samples, markdown preview samples, debug preLaunchTask marker, restricted workspace-settings, and a Git local-config helper generator with marker scripts.
• Update the top-level VS Code audit README to reflect successful local clone in this pass and refine the initial conclusion to reflect source-audit outcomes and outstanding runtime validation needs.

Testing

• No automated tests were executed as part of this change; the patch provides fixtures and a reproducibility plan intended for manual/CI runtime validation against a built or released VS Code with clean profiles.

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Codex Task