fix: configure ContinuousDeployment for main branch in GitVersion 6

- Set main branch to ContinuousDeployment mode (equivalent to v5 MainLine)
- Produces clean versions on main (e.g. 0.15.16) without pre-release suffix
- Fixes NuGet rejection of bare numeric pre-release labels (0.15.15-6)

Author: JerrettDavis

GitVersion.yml

@@ -5,3 +5,7 @@ commit-message-incrementing: Enabled
 major-version-bump-message: '(?m)^[a-z]+(?:\([\w\s\-,/\\]+\))?!:|(?m)^\s*BREAKING CHANGE:'
 minor-version-bump-message: '(?m)^feat(?:\([\w\s\-,/\\]+\))?:'
 patch-version-bump-message: '(?m)^(?:fix|perf)(?:\([\w\s\-,/\\]+\))?:'
+
+branches:
+  main:
+    mode: ContinuousDeployment