feat(history-panel): add branch visibility modes and richer refs

Adds branch visibility modes to the history panel and remote branches.
A data model supports commits and refs including local and remote.
UI tweaks add compact ref chips and a new details panel.

- Implement focus/local/all/custom modes for branch visibility
- Introduce CommitBranchDecoration and CommitRefSummary types
- Wire remote branches and ahead/behind data to UI

src/App.svelte

@@ -4929,8 +4929,11 @@
           {commits}
           {selectedCommitHash}
           {localBranchNames}
+          remoteBranchNames={remoteBranches.map((branch) => branch.name)}
           activeBranch={status?.current_branch ?? ""}
           activeUpstream={status?.upstream ?? ""}
+          activeAhead={status?.ahead ?? 0}
+          activeBehind={status?.behind ?? 0}
           repositoryKey={activeRepoPath}
           {hasRepository}
           {isBusy}