Pr Storyteller

Generate PR text (title, description, test plan) for the current branch. Do not open a PR or push anything — only output markdown text.

Steps:

1. Determine the base branch: use $1 if provided. Otherwise try main; if main does not exist as a branch, use master.
2. Run git merge-base <base> HEAD to get the merge-base commit.
3. Run git log <merge-base>..HEAD --no-merges --pretty=format:%s to get commit subjects since the merge-base.
4. Run git diff <merge-base>..HEAD --stat to get the changed files and diff stat.
5. From these, generate:
   • Title: a single-line, conventional-commit-style summary of the overall change (e.g. feat: add X, fix: correct Y). Base it on the overall theme of the commits, not just the first commit.
   • Description: short bullet points synthesized from the commit subjects. Group related/overlapping commits into single bullets instead of listing every commit verbatim. Keep it factual — only describe what the commits and diff actually say.
   • Test Plan: a checklist inferred mechanically from the file types/areas touched in the diff stat. Examples of the mapping to apply:
     • Test files changed (*test*, *spec*) -> "Run the test suite"
     • Config/dependency files changed (package.json, *.lock, requirements.txt, Cargo.toml, go.mod, Dockerfile, CI config) -> "Verify build/install still works"
     • UI/frontend files changed (.tsx, .jsx, .vue, .css, .html) -> "Manually verify affected screens"
     • Docs changed (.md, docs/) -> "Proofread rendered docs"
     • Otherwise/generally -> "Review the diff for correctness" Keep items generic and mechanical — do not invent specific test scenarios that require domain knowledge of the change.
6. Output the final result as markdown ready to paste directly into a PR, in this shape:

## Title
<title>

## Description
- <bullet>
- <bullet>

## Test Plan
- [ ] <item>
- [ ] <item>

Do not include any other commentary before or after the markdown output.