PHLEGM v8 revision 82: checkpoint / revision metadata synonyms.

- checkpoint.current and revision.current are aliases of the same value.
- Single runtime storage: gMasterCheckpoint; no second revision counter.
- checkpoint.current is authoritative when BOTH keys appear. An explicit
  blank checkpoint.current hides the GUI revision suffix, irrespective of
  revision.current or declaration order.
- revision.current can be supplied by itself as a compatible alias.
- Derived placeholders <$checkpoint> and <$revision> refer to one number.
- GUI title remains ucwords(<$proper>) v<$version> [r<$checkpoint>].
- The title has no r suffix when the value is blank or absent.
- The PHLEGM build metadata now identifies this checkpoint as 82.
- Existing CHOP, End-User packaging retention, and compiler scripts unchanged.
- Website PHP filename parser is not changed (user already fixed it).

Regression checks: tests/PHLEGM-Revision-Alias.Tests.ps1.
Native FreeBASIC compilation and GUI runtime still require testing.
