build: parse beta/rc/devel PostgreSQL version strings

The meson build derived the major version with .split('.')[0].to_int(), which
fails on pre-release version strings such as '19beta1' (no dot, non-numeric
suffix). Strip a trailing beta/rc/devel suffix before converting, so the
extension configures against pre-release PostgreSQL for testing. Release
versions are unaffected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: OffgridwithJD

meson.build

@@ -72,7 +72,7 @@ lz4 = dependency('liblz4', required: false)
 z = dependency('zlib')
 zstd = dependency('libzstd', required: false)
 
-major_version = version.split(' ')[1].split('.')[0].to_int()
+major_version = version.split(' ')[1].split('.')[0].split('beta')[0].split('rc')[0].split('devel')[0].to_int()
 
 fetools = 'fetools/pg@0@'.format(major_version)