#1385 Merge stable into develop

Merging stable into develop after merging pull request #1293.

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Summary by cubic

Fixes generators, transforms, and checks targeting the wrong branch, and prevents BranchNotFoundError when run without an explicit branch.

• Runs without --branch now target the configured default_branch (INFRAHUB_DEFAULT_BRANCH, main by default) instead of the local Git checkout's active branch. Set INFRAHUB_DEFAULT_BRANCH_FROM_GIT=true to keep following the local Git branch.
• Branch resolution now reads from the operation's root directory instead of the process working directory when default_branch_from_git is enabled.