Aligns the last detail page with the 7 already migrated in PR #3510.
The hand-rolled MemberBreadcrumb (workspace-name root, custom gap-1.5,
missing text-foreground on the leaf) is replaced by the shared
BreadcrumbHeader; the workspace avatar/name no longer renders, and
MemberDetailSkeleton is reshaped to match (segment + chevron + leaf,
no workspace-name placeholder).
- Add wsPaths.members() so the segment href resolves; update
paths.workspace() shape and the relevant unit tests.
- Drop the now-unused `detail.workspace_fallback` i18n key from all
three locale files (en/zh-Hans/ko); `members_breadcrumb` and
`breadcrumb_fallback` remain.
Refs MUL-2851 (parent: MUL-2850).
Co-authored-by: multica-agent <github@multica.ai>
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