AtlasSpigot 26.2 - v6 (branding fixed at the real root cause)

Change from v5 - this is the real fix for the recurring "F3 branding is gone" reports:

Found the actual source of truth: a Brand-Name jar manifest attribute in leaf-server/build.gradle.kts, which ServerBuildInfo.brandName() reads and which every brand-related code path traces back to - the early [bootstrap] startup line, the console banner, getServerModName()/F3, and the config default. It was still literally "Leaf" in the build config, regardless of any runtime config file.

Fixed there directly. This means branding is now correct even with zero config files present - verified by booting with no config directory at all (only the jar + eula.txt) and confirming every brand-related log line said AtlasSpigot, not just the ones that were already fixed via config in v5.

Deliberately left alone: Brand-Id (an internal identifier used for plugin compatibility checks against Paper/Gale/Pufferfish/Purpur, not display text - changing it risks breaking plugin detection for no visible benefit), Specification-Vendor (honest attribution to the actual authors, Winds Studio), and all LICENSE.md/copyright content (an MIT license requirement, not branding).

See README for the full explanation and source-patches/build-manifest-brand-fix.diff for the exact change.