Pending changes UI: show apply outcomes

[jamesrochabrun]

Parent: #398

Depends on: the apply outcome model from the fuzzy apply issue.

Goal

Show users what happened during pending edit preview generation: how many edits applied, which ones matched fuzzily, and which failed or were rejected.

Implementation Notes

Target area: app/modules/AgentHubCore/Sources/AgentHub/UI/PendingChangesView.swift.

Consume PreviewResult.outcomes from PendingChangesPreviewService and render compact, actionable status near the pending diff.

Expected UI behavior:

• summary chip like Applied 3/4, with counts for exact/fuzzy/failed/rejected when present
• fuzzy match rows include confidence and matched line range
• failed rows include the reason
• rejected artifact-contamination rows show a distinct error state and offending markers

Keep the diff preview itself focused; do not add a large explanatory panel unless there are failures/rejections.

Acceptance Criteria

• Clean exact edits do not add noisy UI.
• Partial MultiEdit previews visibly show applied count and failed edit reason.
• Fuzzy previews show that a fuzzy match was used and where it matched.
• Rejected previews show a clear rejection banner and cannot be accepted as if clean.

Tests

Add view-model or SwiftUI-friendly tests where practical. At minimum, keep PendingChangesPreviewServiceTests covering the data contract consumed by the UI.