Author a custom slash command Claude Code will run the same way every time

Write a custom slash command for Claude Code as a single markdown file, ready to save at .claude/commands/review-pr.md. The filename determines the command name Claude Code exposes, so name the file to match exactly how the command should be invoked, and if it belongs under a namespaced subdirectory rather than the flat commands folder, say so and explain why grouping it improves discovery.

WORKFLOW TO TURN INTO A COMMAND
Whenever a pull request is ready for review, fetch the diff against main, run the project's lint and test commands, and produce a structured review of correctness, tests, and scope — currently done by retyping a long prompt each time.

ARGUMENTS THIS COMMAND ACCEPTS
An optional PR number or branch name; if omitted, review the current branch against main.

STRUCTURE THE FILE AS
1. YAML frontmatter with: a description field stating what the command does and when to reach for it, an argument-hint field showing the expected shape of the passed-in text in the exact form a user would type it, and an allowed-tools field naming only the tools this workflow actually needs — do not grant Bash or Write access to a command that only reads and reports.
2. Below the frontmatter, the command body written as a direct instruction to Claude Code, substituting the passed-in argument wherever it belongs, and using positional references if the workflow genuinely needs more than one distinct value rather than one free-text blob.
3. An explicit output contract at the end of the body: the exact section headers or format the command must produce every time it runs, so invoking it twice on different input produces comparably-shaped output, not two differently organized answers.

CONSTRAINTS
- The command must do one workflow well, not several loosely related ones behind one name. If the workflow described above is actually two distinct jobs, say so and propose two separate command files instead of forcing one.
- If the workflow needs project-specific context that will not exist in every repo this command might later be copied into, such as a specific test command or file path, make that a documented argument or a clearly marked placeholder, not a hardcoded assumption.
- Do not have the command silently take an action with side effects, such as committing, pushing, or deleting, unless No — this command only reads and reports, it never commits or pushes. explicitly says it should — and even then, end the body with an instruction to state what it is about to do before doing it.
- If the workflow would benefit from a model cheaper or faster than the main conversation is using, such as a purely mechanical formatting pass, note that as an optional model field in the frontmatter rather than leaving every invocation on the default model by default.

OUTPUT
The complete markdown file content, frontmatter included, ready to paste as-is. After the file, one sentence on which command already listed in .claude/commands/ currently has commit.md and changelog.md., if any, this new one might overlap or conflict with by name or by purpose.