tp: report verbs load errors in HCA diagnostics

[cwschroeder]

When the verbs library cannot load, the port selector discards that error and HCA reports NoRoceDevice. This patch retains LibraryUnavailable or MissingSymbol through the existing port exchange and reports the load failure when no devices were selected. The message points to the RDMA userspace installation.

The exchange still completes before HCA reports the local failure. Explicit HCA lists, successful empty-scan behavior and transport fallback are preserved. The error records only Verbs.open failures; device/port query diagnostics are outside this change.

Validation on 8f75a6aa22c9c71d1342bbf0d914a67ae3a5318e:

• Negative control: exactly two failures, expected LibraryUnavailable/MissingSymbol but found NoRoceDevice; 1460 passed, 8 skipped.
• Local Zig 0.17.0 Linux safe cross-build: 5/5 passed; build-only, without a mailbox image.
• Whole-tree format and whitespace passed. Lean: 517 base, 517 candidate, zero new. Final source review found no material issue.
• Candidate CI: all No GPU commands passed, and all six current-head checks are green.

Based on upstream PR ashhart#636 at 46161ac46a4448e4b7179fba84e3554537a43319; main 6ee828c24bf802cdd73507d6fc60bb27a82c0d66. Addresses the HCA diagnostic report. No GPU, model or RDMA run.

Patch and source/compiler/binary hashes. The patch also passes apply-check over the separate CLI fix at 602a0fd; no combined runtime qualification.