feat(windows): add default root support

[austinconnor]

Summary

• add Windows-aware home, AppData, Program Files, and filesystem-root handling for profile root resolution
• add Windows baseline candidates for package-manager roots, editor extensions, MCP configs, and browser extension profiles
• preserve native package paths on Windows so the full test suite passes from this branch alone
• document Windows support, inventory roots, and deployment examples

Fixes #2.

Verification

• go test ./...
• go run ./cmd/bumblebee selftest
• go run ./cmd/bumblebee roots --profile baseline
• GOOS=linux GOARCH=amd64 go test -c -o NUL for every package
• GOOS=darwin GOARCH=amd64 go test -c -o NUL for every package