windows menubar: Claude quota panel reads ~/.claude/.credentials.json from the Windows home only — empty for WSL-only installs

Found while building #1059 (WSL discovery). windows/src-tauri/src/plan.rs reads ~/.claude/.credentials.json from the Windows home for the Claude quota/plan panel. A user whose Claude Code lives entirely inside WSL (the #1059 scenario) gets usage data via the CLI (once #1059 lands) but an empty Plan panel, because the credentials sit in \\wsl$\<distro>\home\<u>\.claude\.

Fix direction: after #1059, reuse src/wsl.ts's running-distro home enumeration from the tray app (or have the CLI expose the resolved credential path), with the same running-only/never-boot-a-stopped-distro rule and read-only access. Out of scope for #1059 itself.