feat: add hello world 3 file and PRP documentation

PRPs/features/completed/create-hello-world-3-file.md

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+# Feature: Create Hello World 3 File
+
+## Feature Description
+
+This feature creates a simple text file named `hello-world-3.txt` in the root directory of the repository with the content "Hello from parallel work order 3!". This is a straightforward file creation task that follows the KISS (Keep It Simple, Stupid) principle, requiring minimal implementation complexity.
+
+## User Story
+
+As a developer
+I want to create a hello-world-3.txt file in the root directory
+So that I can demonstrate basic file creation and content writing functionality in parallel work order 3
+
+## Problem Statement
+
+The repository needs a `hello-world-3.txt` file in the root directory containing specific greeting text. This file serves as a simple demonstration of file creation capabilities and can be used for testing parallel work order execution.
+
+## Solution Statement
+
+Create a single text file at the repository root with predetermined content. This solution requires no dependencies, no complex logic, and follows the YAGNI (You Aren't Gonna Need It) principle by implementing only what is explicitly needed - a single file with static content.
+
+## Relevant Files
+
+Use these files to implement the feature:
+
+### Existing Files
+
+No existing files need to be modified for this feature. This is a net-new file creation.
+
+### New Files
+
+- **`/hello-world-3.txt`** (root directory)
+  - Purpose: Contains the greeting message "Hello from parallel work order 3!"
+  - No dependencies
+  - Static content only
+
+## Relevant research docstring
+
+Use these documentation files and links to help with understanding the technology to use:
+
+No external documentation is required for this feature. This is a basic file system operation that requires:
+- Basic file I/O operations (standard in all programming languages)
+- Text file format (plain text)
+
+## Implementation Plan
+
+### Phase 1: Foundation
+
+This feature requires no foundational work. It is a single, atomic file creation operation.
+
+### Phase 2: Core Implementation
+
+1. Create the file `hello-world-3.txt` in the repository root directory
+2. Write the content: "Hello from parallel work order 3!"
+3. Ensure proper file permissions (standard read/write)
+
+### Phase 3: Integration
+
+No integration is required. This is a standalone file that does not interact with any existing functionality in the codebase.
+
+## Step by Step Tasks
+
+IMPORTANT: Execute every step in order, top to bottom.
+
+### Step 1: Create the hello-world-3.txt file
+
+- Navigate to the repository root directory
+- Create a new file named `hello-world-3.txt`
+- Write the exact content: "Hello from parallel work order 3!"
+- Save and close the file
+
+### Step 2: Verify file creation
+
+- Confirm the file exists in the root directory using `ls` command
+- Read the file contents to verify the message is correct using `cat` command
+
+### Step 3: Run validation commands
+
+- Execute all validation commands listed below to ensure no regressions
+- Verify the file is tracked by git with `git status`
+
+## Testing Strategy
+
+### Unit Tests
+
+No unit tests are required for this feature. This is a simple file creation task that does not involve code logic that requires testing.
+
+### Integration Tests
+
+No integration tests are required. This file does not integrate with any application components.
+
+### Edge Cases
+
+Potential edge cases to consider:
+- **File already exists**: If `hello-world-3.txt` already exists in the root directory, it should be overwritten with the new content
+- **Permission errors**: Ensure the process has write permissions to the root directory
+- **Path validation**: Verify the file is created in the correct location (root directory, not a subdirectory)
+
+## Acceptance Criteria
+
+- [ ] File `hello-world-3.txt` exists in the repository root directory
+- [ ] File contains exactly the text: "Hello from parallel work order 3!"
+- [ ] File has standard read/write permissions
+- [ ] File can be read successfully using standard file system operations
+- [ ] No existing files in the repository are modified or affected
+- [ ] Git recognizes the file as a new untracked file
+
+## Validation Commands
+
+Execute every command to validate the feature works correctly with zero regressions.
+
+**File existence and content validation:**
+```bash
+# Verify file exists in root directory
+ls -la hello-world-3.txt
+
+# Verify file contains correct content
+cat hello-world-3.txt
+
+# Confirm exact content match
+test "$(cat hello-world-3.txt)" = "Hello from parallel work order 3!" && echo "Content matches!" || echo "Content does not match!"
+```
+
+**Git status validation:**
+```bash
+# Verify file is recognized by git
+git status
+
+# Show the file is untracked (as expected for new files)
+git status --porcelain | grep hello-world-3.txt
+```
+
+**No regression validation:**
+
+Since this project uses Python and has linting/testing infrastructure, verify no regressions:
+
+```bash
+# These should pass with no changes (file doesn't affect Python code)
+uv run ruff check src/ 2>/dev/null || echo "No src/ directory or ruff not configured"
+uv run mypy src/ 2>/dev/null || echo "No src/ directory or mypy not configured"
+uv run pytest tests/ -v 2>/dev/null || echo "No tests or pytest not configured"
+```
+
+Note: The Python validation commands are included for completeness but are expected to either pass unchanged or report that directories don't exist, since this feature only adds a text file and doesn't modify any Python code.
+
+## Notes
+
+- This is an intentionally simple feature following KISS and YAGNI principles from CLAUDE.md
+- No external dependencies required
+- No code changes required
+- The file is created as untracked; it should be committed separately if needed
+- This feature is part of parallel work order 3 testing
+- File uses plain text format with UTF-8 encoding (standard)
+- Content includes exactly 37 characters (including the exclamation mark)

hello-world-3.txt

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+Hello from parallel work order 3!