Context: The Tangled fork (tangled branch) is a git-over-SSH backend; the upstream SettingView.addFavicon / addLogo flows call the Octokit REST API directly (PUT /repos/{owner}/{repo}/contents/{path}) when the user clicks "Apply settings to site" in Appearance settings. A Tangled connection has no Octokit, so v1 defers this (decision 10 in docs/notes/tangled-fork.md).

v1 behavior: on PublishPlatform.Tangled, skip the favicon/logo writes and show a Notice (settings other than favicon/logo still apply via updateEnv).

Suggested follow-up path (this issue):

1. Route the icon/logo writes through the user garden connection's updateFile (they are just src/site/favicon.svg / src/site/logo.* repo files) instead of the raw Octokit calls in SettingView.addFavicon/addLogo.
2. Reuse the existing "Content base directory" prefixing already applied by the path builders in src/publisher/paths.ts.
3. Keep the GitHub path unchanged; add a small abstraction (e.g. a method on RepositoryConnection) so both backends share one code path.

Relates to: Tangled fork plan (docs/notes/tangled-fork.md).