Prepare v0.5.2 release

[mjc]

This adds the v0.5.2 changelog section and updates the release notes to cover:

• faster retrying of missing articles via per-backend stat_missing probing
• response write metrics wiring to runtime config
• backend DNS lookups honoring TTL
• retry-path routing and guard hardening

The branch has been pushed and is ready for review.

Summary by CodeRabbit

• New Features
  • Added per-backend STAT probing to prefetch missing articles after 430 responses.
  • Added queue backpressure routing with configurable thresholds.
  • Added optional response-write and client-writer lock metrics.
  • Added CPU pinning runtime support.
• Bug Fixes
  • Improved TUI session and connection-count accuracy.
  • Fixed DNS TTL handling and user-active connection counts.
  • Hardened retry routing and reduced TUI rendering overhead.
• Documentation
  • Updated operator, Docker, and Nix configuration examples.
• Chores
  • Released version 0.5.2.

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• CHANGELOG.md
• Cargo.toml

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---

📝 Walkthrough

Walkthrough

Version 0.5.2 release metadata, configuration examples, and operator documentation were updated for per-backend STAT-missing probing, queue backpressure, metrics intervals, and deployment settings across Docker, Docker Compose, and Nix.

Changes

v0.5.2 Release Configuration

Layer / File(s)	Summary
Release versioning and changelog Cargo.toml, CHANGELOG.md	The package version changed from 0.5.1 to 0.5.2. The changelog documents the release additions, changes, fixes, and documentation updates.
Configuration schema and examples config.full.toml, docs/operator/configuration.md	Configuration references and examples describe proxy metrics intervals, queue backpressure thresholds, all_busy_sleep_ms, backend stat_missing, and STAT_MISSING.
Docker and Nix deployment examples Dockerfile, docker-compose.yml, docs/operator/operations.md, nix/module.nix	Deployment examples enable or document stat_missing for backend servers. Operations documentation describes STAT probing when a backend returns 430.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to f0f6f

No actionable release-documentation issue remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: preparing the v0.5.2 release through the version bump and release documentation updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

⚔️ Resolve merge conflicts 💡

• Resolve merge conflict in branch mjc/release-v0.5.2

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch mjc/release-v0.5.2

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_{A rabbit records the release in a neat little line,
STAT probes and queue limits now align,
Metrics intervals sit clear in their place,
Docker and Nix show the configured base,
Version 0.5.2 is ready to shine.}

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@CHANGELOG.md`:
- Line 10: Confirm and correct the release date in the changelog header "##
[0.5.2] - 2026-06-10" to match the actual release/PR date; update that header to
the correct date (e.g., 2026-06-11 if the PR metadata is authoritative) or
verify with the release manager and set the date accordingly so the "## [0.5.2]
- ..." line is accurate.

In `@rust-toolchain.toml`:
- Line 2: The toolchain bump in rust-toolchain.toml (channel = "1.96.0") is fine
but the RustSec advisory lookup failed due to an unauthenticated GitHub API
call; add a step to run cargo audit (or RustSec) in CI or locally with
authenticated access: add a CI job that runs cargo audit against the workspace
after the toolchain bump and ensure the job provides a valid GitHub token (e.g.,
GITHUB_TOKEN) or points RUSTSEC_ADVISORY_DB at a checked-out advisory-db mirror
so the RustSec lookup can complete without HTTP 401 errors.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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📒 Files selected for processing (9)

• CHANGELOG.md
• Cargo.toml
• Dockerfile
• config.full.toml
• docker-compose.yml
• docs/operator/configuration.md
• docs/operator/operations.md
• nix/module.nix
• rust-toolchain.toml

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@CHANGELOG.md`:
- Around line 21-26: The three bullet points in the "Added" section (lines
23-25) all begin with the word "Added", creating repetitive sentence structure
that reduces readability. Reword one or more of these bullet points to use
alternative phrasing such as "is now available", "provides", or similar
constructions that convey the same meaning while varying the sentence structure.
For example, rephrase the second bullet point about CPU pinning or the third
about rustix-based affinity handling to start differently, maintaining the
content's clarity and technical accuracy while improving the overall flow of the
changelog entry.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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Review profile: ASSERTIVE

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Run ID: 9b49fc4e-9c01-418f-b572-43b38b785494

📥 Commits

Reviewing files that changed from the base of the PR and between 3f30d7d and 70b669f.

⛔ Files ignored due to path filters (1)

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📒 Files selected for processing (8)

• CHANGELOG.md
• Cargo.toml
• Dockerfile
• config.full.toml
• docker-compose.yml
• docs/operator/configuration.md
• docs/operator/operations.md
• nix/module.nix