Reproducer projects for bug reports, check_run for code samples, and a COM Interfaces section

[KubaO]

Puts a reproducer project behind every bug report, runs documentation samples and checks what they print, and adds a Custom Enumerators page and a COM Interfaces section.

• bugs: scripts/bug_repro.mjs (new) gives each entry of BUGS-TO-REPORT.md a reproducer under bugs/<slug>/: a source tree, the .twinproj packed from it, and a repro.json saying what a reproduction looks like. new can start from a template, such as a form with a WebView2 control; verify asks the newest beta whether each still reproduces; file moves a filed entry to bugs/filed/. 45 entries have one: 28 filed, each citing its GitHub issue, and 17 queued.
• scripts: tbrun --llvm compiles the probe with LLVM, and --exe also builds it and runs the exe. tbrun exits 5 when the probe ended before it returned, and 6 when the exe exited non-zero or outlived --timeout. tbbuild and check_examples gain --build and --llvm, because a compile asks only the front end and code generation runs in a build. Each IDE gets a temp folder of its own: builds sharing one failed to write the type library in 8 of 192, against 0 of 192 with a folder each.
• check_examples: check_run (new) builds and runs a statement sample and compares what it prints with the page: a trailing comment on a Debug.Print line, or the comment lines under ' Output:. A Sub Main in a class slot is now a finding, and the Form, MDIForm and NamedPipeServer samples that had one are split.
• docs: a Custom Enumerators page ([Enumerator], writing an IEnumVARIANT, what For Each calls) and a COM Interfaces section, whose first page, IEnumVARIANT, gives each method's contract and a full enumerator: 914 to 917 pages. InStr, InStrRev and those two pages carry the first check_run samples.
• docs, corrections:
  • InStr and InStrRev list their return values in the order they apply, as VB6 and BETA 995 give them; InStrRev raises 94 on Null.
  • Line's F fills with the outline colour and B alone with FillColor and FillStyle, on all six drawing surfaces.
  • Forms(i) can return another object, depending on the expression around it. Static with a constructor fails only when the class is declared later.
  • The LLVM page says an error is lost between procedures when either is LLVM-compiled, and that a handled Err.Raise in an LLVM procedure reads back as &HEAEAEA01.
  • The WebView2 header pages warn that For Each over headers crashes in BETA 995, and name GetHeader and Contains instead.
• docs, rule: the docs state what twinBASIC does, never that it was measured, probed or observed; the pages that broke the rule are reworded.

bug_repro verify and check_run need a twinBASIC install, so they stay outside every gate and CI, like examples.bat. check_run's probes need none and run in test.bat.