[tib8]

A new separate branches column with more compact branch labels, so the message text area is less noisy:
(some related PRs also visible on this screenshot)

Adds an opt-in BRANCHES item as the first option under the history view's SHOW COLUMNS menu. Enabling it displays a resizable column before the graph and saves its visibility and width per repository.

• Reuses the existing colored branch badges. The current branch takes priority, followed by local and remote branches.
• Combines matching local and remote refs on the same commit into one badge with both icons. Additional distinct labels appear as a +N count outside the badge.
• Truncates long names with ... to fit the available column width, reserving count space only when needed. Tooltips retain every full branch name.
• Connects branch-tip badges to their commit dots with a matching-color horizontal line: fully opaque for the active branch, 70% opaque otherwise.
• Shows a 70%-opacity branch badge while an unlabeled commit row is hovered anywhere or selected, including multi-selection. These badges use branch identity carried along the graph lane and do not draw connectors.
• Hides duplicate branch badges in the message area while the column is shown; tags remain visible after the subject. Hiding the column restores the original layout.

This is a standalone port onto develop and does not require the separate Working Directory row or history-column reordering changes.

Validation on Windows with .NET 10:

dotnet format src/SourceGit.csproj --verify-no-changes --no-restore
dotnet run --project tests/BranchColumnChecks --no-restore -p:UsedAvaloniaProducts= -- --render

Formatting verification passed. All 52 branch-column checks passed, covering grouping, Unicode truncation, tooltips, whole-row hover and selection, connector geometry, header dragging, saved settings, and layout restoration. The rendered history view was also inspected.