PHLEGM v8 - revision 85: checkpoint.current canonical numeric normalization

- Source master metadata stores `checkpoint.current=85` (without a prefix).
- Native FreeBASIC master loader accepts `85`, `r85`, or `R85` and stores `85`.
- GUI title revalidates the shared checkpoint before emitting `Phlegmulator v8 r85`.
- PowerShell's master reader normalizes both aliases in the returned Values table.
- A master timestamp rewrite also normalizes any existing r/R-prefixed metadata on disk.
- `revision.current` stays a compatibility alias; checkpoint.current takes precedence.
- New filenames emit `-r85`; old `-85` filenames remain readable.
- Empty checkpoint values omit the GUI revision suffix.

Native FreeBASIC compilation and PowerShell execution require an installed toolchain.
