bug(provider-switch): preserve native projection fidelity reports

[Juliusolsson05]

Expected behavior

Carry native projection reports independently from context reduction and restored-draft reports through IPC, operation records and reviewable UI summaries.

Source finding and impact

All three operations consume projection.values but omit projection.report from returned results. switchProvider returns shrinkSummary, which describes context reduction rather than native format fidelity. Callers lose preservation/loss/repair evidence from the projector.

Evidence and environment

Inspected source at 552914f5610518458f944fa1bdaf63f243685bd1 on 2026-09-12 in the local macOS workspace. This finding has not yet been reproduced through a running application or the package integration suite.

• src/main/providerSwitch/switchProvider.ts
• src/main/providerSwitch/duplicateSession.ts
• src/main/providerSwitch/rewindSession.ts

Regression and acceptance

Use a real parser fixture whose native-resume projection reports loss or repair. Verify switch/duplicate/rewind return the report and the client can inspect it even when context reduction reports no shrink.

The resolving PR must protect the observable contract and document any remaining uncertainty. This planning pass makes no runtime changes.

Refs #918; planning finding F14.