Update gittools/actions to v4.4.2 and GitVersion to 6.x

[Copilot]

• Update build.yml: bump gittools/actions/gitversion/setup and execute from v0.13.6 to v4.4.2
• Update build.yml: bump versionSpec from 5.12.x to 6.7.x
• Update GitVersion.yml: rename tag → label for all branch configs (GitVersion 6.x renamed this property)
• Update GitVersion.yml: capitalize increment: patch → increment: Patch (GitVersion 6.x uses PascalCase)
• Fix: rename master → main (built-in v6 key matching ^master$|^main$, no regex needed)
• Fix: add mode: ContinuousDelivery to main branch to restore beta pre-release label behavior (in v6, ContinuousDeployment on a main branch produces clean semver without labels)

[bastianeicher]

@copilot gitversion is failing with:

Branch configuration 'master' is missing required configuration 'regex'

Please fix this and verify your fix by running gitversion.

[Copilot]

@copilot gitversion is failing with:

...

Fixed in 401fb8d. Two issues were addressed:

1. master is not a built-in key in GitVersion 6.x — the v6 built-in key is main (with default regex ^master$|^main$), so non-built-in keys like master require an explicit regex. Renaming to main resolves the error without needing a regex.

2. ContinuousDeployment mode on a main branch in v6 produces clean semver without pre-release labels — to preserve the beta label behavior from v5, mode: ContinuousDelivery is now explicitly set on the main branch. Verified locally with GitVersion 6.7.0:

   • master branch: 1.0.1-beta.1, 1.0.1-beta.2, … ✓
   • develop branch: 1.0.1-alpha.1, 1.0.1-alpha.2, … ✓