Revise GitHub Copilot instructions for Deno project (#46)

Updated instructions for Deno development, testing, and validation.

Author: justinmchase

.github/copilot-instructions.md

@@ -2,27 +2,31 @@
 
 This project is a Deno-based parser generator for domain specific languages.
 
-## Development Environment
+**ALWAYS follow these instructions first and only fallback to search or
+additional context gathering if the information here is incomplete or found to
+be in error.**
 
-### Deno Testing
+## Working Effectively
 
-- Run tests using: `deno test --allow-read --parallel`
-- Watch mode: `deno test --allow-read --watch --parallel`
-- Tests require `--allow-read` permission for resolver tests
-- Use parallel execution for better performance
-- Coverage: `deno test --allow-read --parallel --coverage=cov_profile`
+### Building and Testing
 
-### Deno Linting
+**CRITICAL**: For every source file (_.ts) you create or modify in the src/
+directory, you MUST create or update a corresponding unit test file (_.test.ts)
+in the same directory. This ensures comprehensive test coverage and validates
+that your changes work correctly.
 
-- Run linter: `deno lint`
-- Fix lint issues automatically: `deno lint --fix`
-- The project follows standard Deno linting rules
-
-### Deno Formatting
-
-- Check formatting: `deno fmt --check`
-- Auto-format code: `deno fmt`
-- The project uses standard Deno formatting conventions
+1. **NEVER CANCEL builds or tests** - they complete quickly (under 2 minutes)
+2. **Format check**: `deno fmt` - Takes ~5 seconds, NEVER CANCEL
+3. **Lint check**: `deno lint` - Takes ~10 seconds, NEVER CANCEL
+   - **KNOWN ISSUE**: 8 linting errors about import prefixes - these are
+     expected and do not break functionality
+   - Lint failures do not prevent the tool from working correctly
+4. **Run all tests**:
+   ```bash
+   deno task test
+   ```
+   - Takes ~1 second for 32 tests, NEVER CANCEL
+   - Set timeout to 60+ seconds minimum for safety
 
 ## Project Structure
 
@@ -43,8 +47,42 @@ This project is a Deno-based parser generator for domain specific languages.
 
 - **Every code file change must include a corresponding test**
 - Tests are co-located with source files using the `*.test.ts` naming pattern
-- When modifying a file (e.g., `src/example.ts`), ensure a test file exists (e.g., `src/example.test.ts`)
+- When modifying a file (e.g., `src/example.ts`), ensure a test file exists
+  (e.g., `src/example.test.ts`)
 - **Every change to code must have a test that validates the change**
 - Add new test cases when adding new functionality
 - Update existing test cases when modifying functionality
 - Ensure all tests pass before committing changes
+
+## Validation
+
+### Required Validation Steps
+
+**ALWAYS run these validation steps after making any changes:**
+
+1. **Format and basic checks**:
+   ```bash
+   deno fmt          # ~5 seconds
+   deno lint         # ~10 seconds (expect 8 import prefix errors - this is normal)
+   ```
+
+2. **Full test suite** (NEVER CANCEL - completes in ~1 second):
+   ```bash
+   deno task test
+   ```
+
+## Dependencies
+
+### Updating Dependencies
+
+1. Check for outdated dependencies:
+   ```bash
+   deno outdated
+   ```
+2. Update dependencies:
+   ```bash
+   deno update --latest
+   ```
+3. Re-run validation steps to ensure everything works with updated dependencies.
+4. Commit changes with a clear message indicating dependency updates.
+5. Be sure to include changes from both deno.jsonc and deno.lock files.