add AI Coding Agent instructions for slackecho

.github/copilot-instructions.md

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+# AI Coding Agent Instructions for slackecho
+
+## Project Overview
+**slackecho** is a minimal bash shell script that sends messages to Slack via incoming webhooks using `curl`. The project intentionally keeps scope small: message delivery only, no dependencies beyond curl.
+
+## Architecture & Key Components
+- **Single Script**: `slackecho` - standalone bash executable with no external modules
+- **Integration Method**: Slack Incoming Webhooks (posts JSON payload via HTTP POST)
+- **Minimal Scope**: Script handles message delivery; does not manage authentication, logging, or retries
+
+**Key Design Decision**: This is a "do one thing well" utility meant for shell script integration (e.g., reporting from cron jobs or CI/CD pipelines). Avoid adding features that expand scope beyond message transmission.
+
+## Setup & Execution
+1. **Configuration**: Currently hardcoded `SLACKURL` in the script (TODO: move to external config file)
+2. **Installation**: Copy `slackecho` to a system binary path (e.g., `/usr/local/bin/`)
+3. **Dependency**: Requires `curl` to be installed
+
+## Command Signature
+```bash
+slackecho <message> [username] [channel] [icon]
+```
+
+- `message` (required): Text to send
+- `username`: Slack display name (default: "slackecho-user")
+- `channel`: Target channel (default: "general")
+- `icon`: Emoji icon (default: ":robot_face:")
+
+## Patterns & Conventions
+- **Parameter Handling**: Arguments passed positionally; optional parameters checked with empty string tests (`[ "$2" = "" ]`)
+- **Curl Usage**: Single POST request with URL-encoded JSON payload; output suppressed to `/dev/null`
+- **Error Handling**: Currently minimal—no validation of Slack URL or message content; POST failures silently ignored
+- **Default Values**: All four parameters have sensible defaults defined within script
+
+## Common Modifications
+When adding features, maintain the philosophy of simplicity:
+- **Configuration File**: TODO item suggests moving hardcoded `SLACKURL` to external config
+- **Tests**: Currently N/A; any test framework should be lightweight (e.g., BATS for bash)
+- **Logging**: Not currently implemented; if added, should be optional/minimal
+
+## Important TODOs
+1. Create external configuration file (move `SLACKURL` and defaults)
+2. Add test framework (likely bash-based)
+3. Add code review process
+4. Document contribution guidelines
+
+## References
+- Slack Incoming Webhooks: Uses Slack's webhook JSON format with `channel`, `username`, `text`, `icon_emoji` fields
+- Repository Maintainer: gary@hansenit.solutions