Claude review: samples: rust: rust_driver_pci: use HRT lifetime for Bar

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

This demonstrates the end-state ergonomics beautifully:
```rust
struct SampleDriver<'bound> {
    pdev: &'bound pci::Device,
    bar: Bar0<'bound>,
    index: TestIndex,
}
```

Gone: `#[pin_data(PinnedDrop)]`, `ARef<pci::Device>`, `Devres<Bar0>`, `pin_init_scope`, `bar.access(pdev.as_ref())?`. The driver is dramatically simpler.

The `Drop` impl replaces `PinnedDrop`, which is correct since the struct no longer needs pinning (no `#[pin]` fields).

No issues found.

### PATCHES 20-21: rename 'a lifetime to 'bound

Pure cosmetic rename for consistency. Makes the codebase read clearly -- `'bound` immediately conveys "device binding scope."

No issues found.

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