bug(workspace): change cards omit the repository prefix

[Pulkit7070]

User report

The workspace worker's main change card shows workspace-test.txt, while the Files inspector shows alpha/workspace-test.txt. In a workspace with multiple repositories, the unqualified path does not identify which repository changed.

Expected behavior

Every workspace surface should show the same repository-qualified path.

Steps to reproduce

1. Import a workspace containing repositories named alpha and beta.
2. Delegate a worker task that changes alpha/workspace-test.txt.
3. Compare the completed worker's main change card with the right-side Files inspector.
4. Observe workspace-test.txt in the card and alpha/workspace-test.txt in Files.

Impact

Ambiguous paths increase review risk when different repositories contain files with the same name. The mismatch also makes the change card and inspector appear to disagree.

Acceptance criteria

• Main change cards, Summary, and Files use one repository-qualified path format.
• The repository segment remains visible for renamed and newly created files.
• A multi-repository test covers duplicate filenames in different repositories.

Agent-collected evidence

• Audit date: 2026-09-14
• Platform: macOS, real Electron app, isolated AO data
• Build under test: PR feat: add standalone agent sessions #4851 at f4fd8d7dba24f1e7343fa543af060a3ee1b23399
• Main card: workspace-test.txt
• Files inspector: alpha/workspace-test.txt

[Pulkit7070]

Audit screenshots from the isolated macOS run. The first shows the unqualified path in the change card; the second shows the qualified path in Files.

[Rishet11]

Assigned to @ronishrohan (review #5375)