Update review-protocol dependency and tests (Closes #666)

[octoaide]

Closes #666

Summary

This PR updates the repository to follow upstream changes
introduced after review-protocol 0.19.0 by pinning the
dependency and updating tests that relied on the old API.

What changed

• Pin review-protocol to rev "b0eae25" in Cargo.toml and
  update Cargo.lock accordingly.
• Replace assertions that used AgentInfo.app_name with the
  renamed agent_name in two tests.
• Remove reliance on the private unary_request helper. The
  Linux-only legacy reboot/shutdown tests now exercise the
  public request::Handler API.
• Add an Unreleased note to CHANGELOG.md.

Files touched (high level)

• Cargo.toml (rev pin)
• Cargo.lock (updated)
• src/bin/roxyd/control.rs (test adjustments)
• CHANGELOG.md (Unreleased note)

Validation

• cargo fmt --check passed
• git diff --check passed
• 182 tests passed against a cached post-0.19 protocol
  revision that included the same API changes

Notes

• Exact verification against the b0eae25 commit could not
  be performed here due to blocked outbound GitHub access,
  but the tests were adapted to the API surface changes
  (agent_name rename and unary_request becoming private).
• The Linux-specific tests require Linux CI to run; local
  validation was performed on macOS where applicable.

If you want, I can open a follow-up to run CI on Linux
or adjust the tests further if CI surfaces any platform
specific failures.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.95%. Comparing base (54e1e8f) to head (1bed224).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #667      +/-   ##
==========================================
+ Coverage   81.92%   81.95%   +0.02%     
==========================================
  Files          27       27              
  Lines        4261     4244      -17     
==========================================
- Hits         3491     3478      -13     
+ Misses        770      766       -4     

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