A word starting with a stability letter is read as a pre-release (-arm64 is alpha) #153

Description

Version reads a stability keyword from the start of a word in the suffix even when more letters follow it, so an ordinary word is taken for a pre-release. The a of arm64 or abc reads as alpha, the b of bugfix or build as beta, ga as alpha.

Such a version gets a stability it does not have: it is filtered out by the default stable constraint, matches @alpha/@beta constraints it should not, and sorts by the wrong stability.

Expected: letters that run together form one word and are read to its end. A word is a stability keyword only when the whole word is one (alpha, a, beta, b, rc, dev…), optionally followed by digits (a1, beta2, rc.1). arm64, abc, bugfix, build, ga are not.

Steps to reproduce

use Internal\DLoad\Module\Version\Version;

Version::fromVersionString('1.0.0-arm64')->stability;  // Alpha, suffix `rm64`
Version::fromVersionString('1.2.3.4abc')->stability;   // Alpha, suffix `bc`
Version::fromVersionString('1.0.0-bugfix')->stability; // Beta

Additional context

• The same happens on 1.x; it is not a regression from feat(version): match constraints with DLoad's own version ordering #150.
• The cause is Version::preReleaseFromSuffix(): its keyword regex has no word boundary after the keyword (PreRelease::keywordPattern() followed by optional digits).
• Found while reviewing feat(version): match constraints with DLoad's own version ordering #150, where 1.2.3.4abc now gets the right number 1.2.3.4 but still reads as alpha.