chore(ci): update mbx to 0.6.0

[jdx]

Update the CI wrapper to mr-boxington-action 906ad32aec2915c312aceb21c2354cc8c0548f5f, install mbx 0.6.0, expose the action’s explicit toolchain cache-key input, and regenerate the verified mise.lock metadata.

AI-assisted — Tool: Codex; model: openai/gpt-5; version: unavailable.

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Note

Low Risk
CI-only dependency and cache-key wiring; no application runtime or security-sensitive logic changes.

Overview
Bumps mbx / mr-boxington-action from 0.5.4 to 0.6.0 (new action commit pin and regenerated mise.lock checksums/URLs).

The composite .github/actions/mbx action gains an optional toolchain input and forwards it to both mr-boxington-action steps so cache keys can name the Rust toolchain explicitly.

In the MSRV job, rustup default is dropped after installing the matrix toolchain; toolchain: ${{ matrix.version }} is passed into mbx instead, while checks still run via mbx +${{ matrix.version }}.

^{Reviewed by Cursor Bugbot for commit 35c71e4. Bugbot is set up for automated code reviews on this repo. Configure here.}

Summary by CodeRabbit

• Chores
  • Updated automated build tooling to support selecting a Rust toolchain.
  • Improved testing across supported Rust versions by applying the selected toolchain directly during validation.
  • Updated the underlying build action to its latest version.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Central YAML (base), Organization UI (inherited)

Review profile: CHILL

Plan: Pro Plus

Run ID: 03c264b8-35cd-4ac7-a87b-f4397ed0fd79

📥 Commits

Reviewing files that changed from the base of the PR and between b8d91f4 and 35c71e4.

⛔ Files ignored due to path filters (1)

• mise.lock is excluded by !**/*.lock

📒 Files selected for processing (2)

• .github/actions/mbx/action.yml
• .github/workflows/test-impl.yml

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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📝 Walkthrough

Walkthrough

The MBX composite action now accepts and forwards a Rust toolchain to both mr-boxington invocations. The MSRV workflow passes its matrix version through this input instead of setting it as the default toolchain.

Changes

Toolchain propagation

Layer / File(s)	Summary
MBX toolchain wiring .github/actions/mbx/action.yml, .github/workflows/test-impl.yml	The MBX action adds an optional toolchain input and forwards it to both jdx/mr-boxington-action steps. Both steps use version 0.6.0. The MSRV job passes ${{ matrix.version }} through the new input and no longer sets it as the default toolchain.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 35c71

This CI-only update changes the mbx version and makes Rust toolchain cache keys explicit without changing application runtime behavior. Runner compatibility with the selected action version should remain a routine check, but no incompatibility is established and no actionable merge-blocking risk remains.

Poem

A rabbit carries toolchains bright

Through MBX paths in careful flight
Two Boxington steps now know the way
MSRV versions guide the day
Fresh action pins complete the run

🚥 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 and concisely describes the primary change: updating the CI mbx wrapper to version 0.6.0.
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.

Full details: Docstring Coverage

Explanation

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 files. (2 skipped: 2 unsupported.)

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[github-actions]

Instruction counts

benchmark	trend	instructions	Δ	wall (min)	Δ
markdown	▂▇▇█▁▂▆▇▁▁▇▁▇▂▁▁▁▇▁	338,172,427 → 337,125,325	-0.31%	29.01 → 28.86ms	-0.49%
startup	▇▇▁▁▁▁▇▇▆▆▆▆▆▆▆▆▆█▆	910,947 → 910,267	-0.07%	0.93 → 0.86ms	-7.42%

No instruction-count regression above 1%.

_{Only instruction counts gate. Wall clock is shown for context — on identical hardware it moves 4-20% run to run.}

_{Measured by tak — instruction-counted CLI benchmarks, stored in this repository's git notes.}

Shadow comparison

Parsing mise use -g node@20 against a shadow of mise's committed spec.
Reported, not gated: the shadow grows as the derive learns to express more, so
what to watch is the ratio rather than either column.

framework	stripped binary, bytes
usage	1321264
bpaf	2493280
clap	3101832

framework	instructions, cold parse	vs usage
usage	8345	—
clap	6315248	756x
bpaf	21909169	2625x

                                              min       p01       p10    median
usage-rs: argv -> struct                      408       417       421       426  ns
clap: build tree + parse -> struct         523808    525820    528690    532735  ns
bpaf: build parser + parse -> struct      1589209   1589209   1597525   1617754  ns

usage: argv -> struct                             453 ns      0.45 µs
clap: build tree + parse -> struct             529622 ns    529.62 µs
clap: parse -> struct, tree reused              23969 ns     23.97 µs
clap: build tree only                          328361 ns    328.36 µs

_{35c71e4b90d9 vs b8d91f4ee14e · measured on the runner, not pushed to the history.}