Fix: Use "Roger" instead of "Roger that" per British Army Voice Procedure

[Copilot]

British Army Voice Procedure uses "Roger" as a single-word affirmative reply. "Roger that" is a Hollywood-ism, not proper military protocol.

Changes

• chatrixcd/messages.py: Updated task_start message from "Roger that!" to "Roger!"
• messages.json.example: Updated corresponding example configuration
• CHANGELOG.md: Documented the change

Example

# Before
"Roger that! Executing **{task_name}**... 🫡 This is gonna be good!"

# After  
"Roger! Executing **{task_name}**... 🫡 This is gonna be good!"

The bot now uses authentic military voice procedure while maintaining its personality.

Original prompt

The British Army Voice Procedure only uses "Rodger" as a single word affirmative reply.

There is no "Rodger That" and certainly nothing afterwards, as that comes from Hollywood and would involve a clarification of "Say all again after Rodger. Over" from whomever received it.

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[Copilot]

Pull Request Overview

This PR updates a bot response message to adhere to proper military radio protocol. The change modifies the task start confirmation from "Roger that!" to "Roger!" across the codebase.

• Changed "Roger that!" to "Roger!" in task start messages to follow British Army Voice Procedure
• Updated both the example configuration file and the actual message constants
• Added CHANGELOG entry documenting the change

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
messages.json.example	Updated task_start message template to use "Roger!"
chatrixcd/messages.py	Updated DEFAULT_MESSAGES constant with "Roger!"
CHANGELOG.md	Documented the message protocol correction

[EdGeraghty]

LGTM