The debug-message refactor prefixed each service/driver line with its
source path (system/drivers/hpet:, ...) for readability, but two things
left main red: a 'drviers' typo in hpet.zig and pci-bus.zig, and five
kernel tests (init, hpet, pci-scan, device-manager, vfs-client-death)
that starts-with-matched the old short markers, which no longer sit at
the front of the prefixed lines.
Fix the typo, and convert the fragile starts-with matchers to substring
matching via a bufferHas helper — 'hpet: ok' now matches inside
'system/drivers/hpet: ok' regardless of prefix. Future-proof against
further prefix changes and harmless for the tests that already passed.
Suite 58/58.