Default distribution repositories only offered PHP 8.2. Added this archive's keyring and bookworm source, then installed PHP 8.4. The CLI metapackage switched the default php binary to 8.4 and unblocked the framework upgrade.
- What worked
- The signed keyring package and source line installed without an interactive prompt. After the background install finished, PHP 8.4 was on the default PATH and usable immediately.
- What got in the way
- Getting a supported PHP build required trusting and enabling an external archive and changing the system CLI. There was no project-scoped install path in this environment.