Rejecting a suggestion learned in another folder does not update or retire the entry that supplied it

## Problem

Reads deliberately include sibling scopes, while rejection and supersession writes target only the current exact scope. When a suggestion comes from another folder, the write finds no corresponding entry and silently does nothing. Repeated refusal therefore leaves the learned evidence unchanged; verifier rejection can also keep re-reading the same entry.

## Evidence

Reviewed `main` at `8d93f5b8574f3c7b8c30086d9c817bf7f5d4827d`. Reproduced against the unchanged production source in an isolated Swift package on macOS, with fake transport or temporary stores as appropriate. These checks assert the observed defect; they are not a claim that the full app test suite passed.

1. Record `git status` in scope `/a`.
2. Query the same app and role in `/b`: the candidate is returned from `/a`.
3. Call `recordRejected("git status", in: /b)`.
4. Query again: `evidence.rejected` is still 0.
5. Call `recordRejection(of: "git status", in: /b)` and query again: the candidate still exists.

Both outcomes were reproduced with the production store. The coordinator passes the current surface to `recordRejected`; verifier reporting also receives the current surface.

## Relevant code

- [Sources/UttrflowPredictStore/PredictStore.swift:96](https://github.com/uttrflow/uttrflow-swift/blob/8d93f5b8574f3c7b8c30086d9c817bf7f5d4827d/Sources/UttrflowPredictStore/PredictStore.swift#L96)
- [Sources/UttrflowPredictStore/PredictStore.swift:388](https://github.com/uttrflow/uttrflow-swift/blob/8d93f5b8574f3c7b8c30086d9c817bf7f5d4827d/Sources/UttrflowPredictStore/PredictStore.swift#L388)
- [Sources/UttrflowPredictStore/PredictStore+Verification.swift:11](https://github.com/uttrflow/uttrflow-swift/blob/8d93f5b8574f3c7b8c30086d9c817bf7f5d4827d/Sources/UttrflowPredictStore/PredictStore+Verification.swift#L11)
- [Sources/Uttrflow/Suggestion/SuggestionCoordinator.swift:361](https://github.com/uttrflow/uttrflow-swift/blob/8d93f5b8574f3c7b8c30086d9c817bf7f5d4827d/Sources/Uttrflow/Suggestion/SuggestionCoordinator.swift#L361)

## Fix and acceptance criteria

Preserve source provenance in candidates, or store feedback against an explicit cross-scope identity with well-defined scope semantics. Refusing a borrowed suggestion must affect subsequent ranking in the destination scope; a verifier retirement must not silently update zero rows. Cover cases with and without an existing destination-scope row.

Read PredictStore.swift around lines 96 and 388, then PredictStore+Verification.swift and SuggestionCoordinator.swift around line 361. Reproduce the cross-folder rejection and verifier cases described in the issue, including cases with and without a destination-scope row. Done means borrowed suggestions retain usable provenance or an explicit cross-scope identity, rejection changes later ranking, and verifier retirement does not silently update zero rows.

Written by the indexing model from the issue text.