e2e(pi): managed-image catalog has conflicting authorities

## Investigation Summary

- The exact-candidate [PR #11071 E2E run](https://github.com/NVIDIA/NemoClaw/actions/runs/33915961523) tested commit `0ddc3ea52efe8a5d63099b92f43cbe0a43c88a01`.
- [Pi AMD64](https://github.com/NVIDIA/NemoClaw/actions/runs/33915961523/job/101163750588) failed before checking the qualification receipt because both the inline managed-image catalog and a configured catalog path were present.
- Pi ARM64 was not executed in that run.
- This is separate from #10966. The run did not reach #10966's stale-receipt assertion.
- PR #10996 currently clears the inherited inline catalog and revision in the Pi fixture, which is a candidate fix for this earlier failure.

## Description

The Pi E2E fixture inherits a workflow-provided inline managed-image catalog while also selecting its own checked-in catalog path. NemoClaw correctly rejects the two authorities, so the target stops before it can validate the Pi qualification receipt.

Expected: the Pi fixture selects exactly one managed-image catalog authority and reaches strict receipt validation.

Actual: pre-clean and the test both fail with `the live E2E managed-image catalog has conflicting authorities`.

## Reproduction Steps

1. Run the Pi AMD64 target from workflow run 33915961523.
2. Provide the workflow inline managed-image catalog while the Pi fixture selects its catalog path.
3. Observe the conflict during phase 1, before the receipt assertion.

## Acceptance Criteria

- The Pi target selects exactly one managed-image catalog authority.
- Cleanup uses the same unambiguous authority boundary.
- Add focused fixture coverage for inherited inline catalog values.
- Pi AMD64 and ARM64 both reach the exact receipt assertion.
- Keep #10966 open until both architectures validate receipts tied to the exact candidate.

## Candidate Fix

- [PR #10996](https://github.com/NVIDIA/NemoClaw/pull/10996), authored by @ericksoa, currently contains the two-line Pi fixture cleanup.
- Retain that change only with focused evidence, or split it into a small PR if #10996 cannot be reduced promptly.

Start with the Pi E2E fixture and candidate PR #10996, then reproduce workflow run 33915961523 to confirm the conflicting-authority failure. Done means the fixture and cleanup use one catalog authority, focused inherited-value coverage exists, and both Pi AMD64 and ARM64 reach the exact receipt assertion.

Written by the indexing model from the issue text.