Concurrent AI isolation: env var detection beats parent chain

When Claude Code and Codex run simultaneously in VS Code, AppBotPipe.Spawn uses DETACHED_PROCESS which breaks the Windows parent chain (parent shows as PID 8). Detect AI identity via env vars first: CLAUDE_CODE_ENTRYPOINT (Claude Code VSCode ext), CODEX_HOME (Codex), VSCODE_PID (VS Code host). Fall back to parent chain walk only when env vars are absent. Also: two AIs sharing the same CWD must use SessionJsonl (exact file path) for size/content reads — CWD scan picks the wrong JSONL.

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