Make update banner fork-aware for KKL releases

[baby-joel]

Problem

Running the KKL fork release v0.79.0-kkl.1 shows Pi's update banner:

Update Available
New version 0.79.0 is available. Run pi update

This happened during an isolated mise smoke test using:

[tools]
"github:KnickKnackLabs/pi" = "v0.79.0-kkl.1"

pi --version correctly reports 0.79.0-kkl.1, so the binary is the KKL release.

Likely cause

0.79.0-kkl.1 is a semver pre-release relative to upstream 0.79.0, so a plain semver comparison can incorrectly treat upstream 0.79.0 as newer than the fork release.

Desired behavior

For KKL fork builds, the updater should not offer the same upstream base version as an upgrade. Possible shape:

• treat 0.79.0-kkl.N as current with respect to upstream 0.79.0;
• only flag upstream drift when the upstream base is actually newer, e.g. 0.79.1;
• ideally check KKL releases for fork-build updates, not only upstream releases.

Notes

This is not blocking /side testing, but it makes released-fork smokes noisy and could confuse users into replacing the KKL fork with upstream Pi.