Adds a "Commit Graph Style" option in Preferences > Appearance (Classic stays the default).

The `Avatars` style shows:
- a resizable BRANCH / TAG column with left-aligned refs, connector lines to the commit, a `+N` badge with a dropdown for refs that do not fit, and tooltips for trimmed names
- a resizable GRAPH column with author avatars (or initials) as nodes, small dots for merges, rounded straight lines and lane colored row bands
- a separate COMMIT MESSAGE column, with left-aligned column headers

Also:
- tooltip on graph avatars with author and date
- right-click on column headers opens the history options menu
- align the graph overlay with the rows below the header separator

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

…push' into develop

- Support `ssh://[user@]host[:port]/path` and `user@host:path` remotes (not only `git@host:path.git`)
- Map Azure DevOps SSH remotes (`v3/{org}/{project}/{repo}`) to their web URL
- Restore the HTTPS probe for SSH hosts (`HTTPSValidator.Add` was no longer called since 582c1a2) and treat well-known hosts as HTTPS

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

- `Models.PullRequestPlatform` detects GitHub, GitLab, Gitea, Forgejo/Codeberg, Bitbucket Cloud, Azure DevOps and Gitee, and builds the create-PR page URL with source, target, and (where supported) title/body, including cross-fork PRs
- Per-remote platform override stored in `sourcegit.settings` for self-hosted servers that can not be detected by host name
- `Commands.QueryRemoteHead` to resolve a remote's default branch

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

- Right-click a remote branch while on another branch: `Create PR: <current> → <remote/branch>...`
- `Create PR for upstream ...` (local branch, or the upstream remote branch of current) opens the same dialog, targeting the remote's default branch
- Dialog with searchable target branch, title and description prefilled from commits and the repository's PR/MR templates
- Optionally push the source branch first (with `-u` and a remote choice when it has no upstream)
- Opens the platform's prefilled create page; fields the platform can not prefill are copied to the clipboard
- Asks for the hosting platform when it can not be detected from host name and remembers it per remote

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

…u in history graph

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

…PR dialog

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Create pr dialog