Start-up environment: VERSION(2), SET LIBRARY paths, POPUP(), #INCLUDE loops

[jefflroberts]

Found running a CodeMine application (Shutter Ace) from the IDE; measured in
Visual FoxPro 9 first.

• VERSION(2) answers 2 in the development environment and 0 in a built
  application, and is a number; programs branch on it to find their source.
  The IDE says which it is through a RUNTIME setting.
• SET LIBRARY TO codemine.fll with no folder means the one beside the
  application - the project folder - not the library host's own directory.
• POPUP(cName) answers whether a popup of that name is defined, as well as
  POPUP() naming the active one.
• A header file that includes itself, or two that include each other, are read
  once each rather than forever; the project source finds a header by name
  wherever in the project it sits.

Verification. The ref_popup_named golden (measured), new cases in crates/foxvm/tests/builtins_system.rs and crates/foxvm/tests/directives.rs. The full VM suite, npm run argforms:check, and the runtime, shared, vfp and reference TypeScript tests pass on this branch.

One of several pull requests split out of work on a CodeMine application (Shutter Ace); each stands on main on its own except where it says otherwise.

🤖 Generated with Claude Code

[RandomChirp]

Measured in vfp9.exe: VERSION(2) is the number 2 in the development environment, VERSION(3) is "00", VERSION(5) is 900, VERSION(0) and VERSION(6) are error 11. The golden ref_popup_named.prg agrees with the product, the #INCLUDE loop guard reads each header once, and cargo test -p foxvm is green on a merge with main.

I checked the ordering worry with the RUNTIME setting: vm.setSetting runs inside startSession, after loadFoxVm, so runtimeUi.development set by IdeLayout at import time is seen. The IDE answers 2 and the player 0, as intended.

Review generated with Claude Code (Claude Fable 5.1), run against vfp9.exe and the test suites on a merge with main.