fix: invoke Bun package exec via bun x on Windows

[kjanat]

Summary

• invoke Bun package-exec fallback through the explicit bun x subcommand instead of the bunx hard-link alias
• preserve forced Bun runtime behavior as bun x --bun
• update dispatch labels, documentation, schema text, and regression tests

Why

On Windows, runner resolves executables through PATH and PATHEXT. The standard uppercase .EXE entry can produce bunx.EXE; released Bun versions classify the invocation name case-sensitively and treat that spelling as plain bun, resulting in error: Script not found for an otherwise valid package.

Using bun x avoids depending on alias-name detection and keeps runner compatible with released Bun versions even if the upstream fix lands later.

Fixes #103

Upstream: oven-sh/bun#36826 and oven-sh/bun#36827

Validation

• cargo fmt --check
• cargo test tool::bun::tests — 8 passed
• cargo test exec_uses_each_runtimes_own_primitive — passed
• cargo test --test runtime_override runtime_selects_the_exec_fallback_primitive — passed
• manual Windows reproduction in shoppingmall: patched runner prints → bun x sort-package-json --version, returns exit 0, and reports sort-package-json 4.0.0

A full Windows cargo test run reached 975 passed / 36 failed. The remaining failures are outside this Bun path and are dominated by existing Windows assumptions around absolute resolved executable paths, Unix-style file URIs, and temporary Git commits.

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📝 Walkthrough

Use bun x for Bun package execution

Replace bunx fallback invocations with the explicit bun x subcommand, including forced Bun execution with bun x --bun. This fixes Windows failures where bunx.EXE is treated as bun and produces Script not found.

Update related labels, documentation, schema text, and regression tests. Validate formatting, targeted tests, and Windows execution of sort-package-json.

Walkthrough

The Bun package-execution path now invokes bun x instead of the bunx alias. Forced Bun execution retains the --bun argument. Tests validate executable names and argument ordering. Documentation, help text, schemas, comments, and the changelog now use the updated command.

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

Sequence Diagram(s)

sequenceDiagram
  participant RunCommand
  participant BunTool
  participant Bun
  RunCommand->>BunTool: request package execution
  BunTool->>Bun: invoke `bun x` with package arguments
  BunTool->>Bun: add `--bun` when forced
  Bun-->>BunTool: execute package

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Possibly related PRs

• kjanat/runner#21: Both changes update Bun command execution and include Windows-specific handling.
• kjanat/runner#75: Both changes update Bun execution handling, but this PR changes package execution.
• kjanat/runner#92: Both changes update Bun package execution in the run dispatch path.

Suggested labels: bug, documentation, area: cli

Poem

Bunx sailed out with a Windows frown,
bun x now steers the command down.
Tests check stems and arguments bright,
Docs match the path, precise and right.
Hoist the fix, matey—smooth execution tonight!

🚥 Pre-merge checks | ✅ 7 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Semver Version Bump Validation	⚠️ Warning	Rust source files contain functional changes, but Cargo.toml remains 0.24.0 in both HEAD~1 and HEAD; no version bump is present.	Update the package version in Cargo.toml from 0.24.0 to 0.24.1 for this bug fix, and include that change in the pull request.

✅ Passed checks (7 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title uses the required fix prefix, stays concise, and clearly describes the Bun Windows invocation change.
Description check	✅ Passed	The description clearly explains the Windows failure, the bun x fix, affected documentation, tests, and validation results.
Linked Issues check	✅ Passed	The changes address issue [#103] by replacing bunx with bun x for Windows-safe package execution and adding regression coverage.
Out of Scope Changes check	✅ Passed	The code, documentation, schema, and test updates directly support the Bun invocation fix and contain no unrelated changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 30.00%.
Changelog Update	✅ Passed	Source files changed, and CHANGELOG.md adds a descriptive Fixed entry under ## [Unreleased]. No version bump is present in the PR diff.
Agents.Md Documentation Updated	✅ Passed	No AGENTS.md file exists anywhere in the repository, so the check's prerequisite for a mandatory update is not met.

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