2026-10-12-apphost-repository-paths

AppHost repository-relative asset paths — issue #865

AspireStartupContext now anchors default repository discovery at builder.AppHostDirectory and uses the nearest .git directory or file, including linked-worktree markers. Relative explicit applicationRoot values that were previously accepted now fail validation; supply a nonblank fully qualified path when constructing a context directly. When no root can be discovered, repository-path requests now fail with a helpful error instead of returning a silent relative path, while path-free profile and factory use remains available. Follow the canonical repository-relative assets guide for asset checks and recovery. This behavior change is covered by the pre-1.0 upgrade policy.