A commit added a bullet and an em-dash inside two Write-Host/Write-Info string
literals in scripts/install.ps1. The file has no UTF-8 BOM, so Windows
PowerShell 5.1 (which the bootstrap runs the cached script under) reads it in
the system ANSI code page (CP1252), not UTF-8. The em-dash's UTF-8 tail byte
decodes to a smart close-quote (U+201D) that the tokenizer treats as a string
delimiter, prematurely closing the string and desyncing the parser -- surfacing
as the reported cascade of syntax errors at lines 1619/1770 and aborting the
Windows GUI installer before it does anything.
Non-ASCII bytes in '#' comments are harmless (skipped to end-of-line), so the
file carried em-dashes in comments for months; only the two chars in code
broke it. Convert all non-ASCII to ASCII equivalents (em-dash -> '--', already
this file's own comment convention; bullet -> '-') and add a source-level test
locking the pure-ASCII invariant, since Linux CI cannot run the PS installer.
Fixes#66994Fixes#67000
97249cfc8a