Add contributing guide

.rtc-wallet

@@ -0,0 +1 @@
+RTC0a1c0ce2204390bc49ecf9780fe894da9dc3d92c

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+# Contributing
+
+Thanks for taking time to improve Fuel Agent Kit. This guide covers the local
+setup, validation commands, and pull request expectations for contributors.
+
+## Local Setup
+
+1. Install Node.js 18 or newer.
+2. Install package dependencies:
+
+   ```bash
+   npm install
+   ```
+
+3. Build the package:
+
+   ```bash
+   npm run build
+   ```
+
+## Development Workflow
+
+Create a branch for each change:
+
+```bash
+git checkout -b my-change
+```
+
+Use focused commits and keep each pull request scoped to one bug fix, feature,
+or documentation update. Before opening a pull request, run the same checks used
+by the project:
+
+```bash
+npm run ci
+```
+
+If you only need a narrower check while iterating, these scripts are available:
+
+| Command | Purpose |
+| --- | --- |
+| `npm run build` | Builds the package with tsup |
+| `npm run test` | Runs the Vitest test suite |
+| `npm run lint` | Type-checks the project |
+| `npm run check-format` | Checks Prettier formatting |
+| `npm run check-exports` | Validates package exports |
+
+## Code Style
+
+- Write TypeScript that passes the existing `tsconfig` checks.
+- Format changed files with Prettier.
+- Prefer small functions with explicit parameter types for exported APIs.
+- Keep wallet, model-provider, and network errors actionable for users.
+- Do not commit generated build output unless maintainers ask for it.
+
+## Security
+
+Fuel Agent Kit works with wallet private keys and model provider API keys. Never
+commit secrets, test keys with real funds, or screenshots that expose private
+credentials. Use environment variables or a local secret manager when testing.
+
+## Pull Requests
+
+When opening a pull request, include:
+
+- a short summary of the change
+- the issue number, if one exists
+- the commands you ran to validate the change
+- screenshots or logs for user-facing behavior, when useful
+
+For larger changes, describe the tradeoffs or compatibility impact so reviewers
+can focus on the important decisions.