docs: open up contributing — agents, platform, suite all welcome

Author: yunhao-j

CONTRIBUTING.md

@@ -0,0 +1,38 @@
+# Contributing to CoderCup
+
+Thanks for helping make the benchmark better. All kinds of contributions are welcome — new agents, platform improvements, bug fixes, stronger test plans, task ideas.
+
+## The flow
+
+1. **Fork** the repo and create a branch.
+2. Make your change. For site/code changes, make sure the checks pass locally:
+
+   ```bash
+   npm install
+   npm run typecheck   # tsc --noEmit
+   npm test            # vitest
+   npm run build       # static export
+   ```
+
+3. **Open a Pull Request** against `main`. CI runs the same checks automatically.
+4. A maintainer reviews and merges. Merges to `main` deploy [codercup.ai](https://codercup.ai) automatically, so reviews are careful — please keep PRs focused and small.
+
+## What to contribute
+
+| You want to… | Start here |
+|---|---|
+| Enter a new coding agent | [`runners/README.md`](./runners/README.md) + a [new-driver issue](https://github.com/TestSprite/CoderCup/issues/new?template=new-driver.md) |
+| Improve the site / harness / scoring | A regular PR — for larger changes, open an issue first so we can align before you invest time |
+| Strengthen the test suite | Edit the plan JSONs under [`tests/`](./tests); explain in the PR what failure mode the tighter assertion catches |
+| Challenge a published verdict | Open an issue linking the test page on codercup.ai and the artifact (video / recorded steps) that contradicts it |
+| Suggest a task requirement | [Task-suggestion issue](https://github.com/TestSprite/CoderCup/issues/new?template=task-suggestion.md) |
+
+## Ground rules
+
+- **Neutrality is the product.** Changes that could tilt the arena toward any vendor — in the spec, the suite, or the scoring — get extra scrutiny. If your change affects scoring, say so explicitly in the PR.
+- **Never hand-edit published results.** Scores and fixtures are derived from the ledger by scripts; PRs that touch `scores/` or `public/fixtures/` by hand will be asked to go through the pipeline instead.
+- Be a normal, decent human in issues and reviews.
+
+## Questions
+
+We're responsive on [Discord](https://discord.gg/W4JDrZfdB), or email [contact@testsprite.com](mailto:contact@testsprite.com).

README.md

@@ -104,9 +104,13 @@ CoderCup is open to any AI coding agent that runs headlessly on a Linux host thr
 
 ## Contributing
 
-- **Test suite & rubric PRs welcome** — every plan JSON in [`tests/`](./tests) is reviewable; tighten an assertion, propose a new phase surface.
-- **Task suggestions** — want a requirement folded into the next iteration? [Open a task-suggestion issue](https://github.com/TestSprite/CoderCup/issues/new?template=task-suggestion.md).
-- **Bug reports** — [bug template](https://github.com/TestSprite/CoderCup/issues/new?template=bug.md).
+Contributions of every kind are welcome — this benchmark gets better the more people poke at it. See [CONTRIBUTING.md](./CONTRIBUTING.md) for the 2-minute guide. Some ideas:
+
+- **Add a coding agent** — the highest-impact contribution. Any agent that runs headlessly on Linux through a CLI can enter; start from [`runners/README.md`](./runners/README.md) or just [open a new-driver issue](https://github.com/TestSprite/CoderCup/issues/new?template=new-driver.md) and we'll help you wire it.
+- **Improve the platform** — the leaderboard site, the runner harness, the scoring pipeline: PRs for features, refactors, and bug fixes are all fair game.
+- **Tighten the test suite** — every plan JSON in [`tests/`](./tests) is reviewable; strengthen an assertion, challenge a verdict, propose a new phase surface.
+- **Shape the next event** — [suggest a task requirement](https://github.com/TestSprite/CoderCup/issues/new?template=task-suggestion.md) for the next iteration.
+- **Report bugs** — [bug template](https://github.com/TestSprite/CoderCup/issues/new?template=bug.md), or just open a plain issue if the templates don't fit.
 
 ## Support