Claude review: rust: sync: completion: add wait_for_completion_timeout()

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

Patch Review

Clean and straightforward. Wraps the C `wait_for_completion_timeout()` function.

```rust
pub fn wait_for_completion_timeout(&self, timeout: Jiffies) -> bool {
    // SAFETY: `self.as_raw()` is a pointer to a valid `struct completion`.
    unsafe { bindings::wait_for_completion_timeout(self.as_raw(), timeout) != 0 }
}
```

**Minor:** The `// ` trailing comment on line 171 of the import block looks like a rustfmt artifact:
```rust
    types::Opaque, //
```
This appears throughout the series and seems to be an intentional rustfmt workaround to force one-import-per-line. Harmless but unusual.

**Question:** The C function `wait_for_completion_timeout()` returns `unsigned long` - the remaining jiffies if completed, 0 if timed out. Collapsing this to `bool` discards the remaining-jiffies information. For this series that's fine, but the Rust binding might want to return `Option<Jiffies>` (or similar) to expose the full API. This could be a follow-up.

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Generated by Claude Code Patch Reviewer