chore: update PHP to 8.4.26 - #182

• No other file in the tree pins a PHP 8.4.x version. Makefile line 1 is the only match, so nothing still points at 8.4.23.
• Release (release.yml line 75) and CI (ci.yml line 160) both read the version from the Makefile's PHP_VERSION, and both parse the PHP_VERSION = 8.4.26 form correctly.
• The release PHP-binary cache key is php-binaries-<version>, so the bump misses the cache and triggers a fresh make download-php instead of reusing 8.4.23 binaries.
• The goreleaser ldflags set legacy.PHPVersion from PHP_VERSION, so the version the CLI reports tracks the Makefile.

No test in the diff covers this. The only automated check is the Windows build step in ci.yml (around line 160), which downloads php-<version>-windows-amd64.exe from the cli-php-builds release, so it would fail if that asset were missing. The Linux and macOS binaries are only fetched by make download-php during the release workflow. I couldn't check that the php-8.4.26 release assets exist because curl isn't available in the sandbox.

• Commit: 398b316
• Model: claude-opus-5-5