Add ASCII crab mascot to README

[Copilot]

Project lacked visual identity. Added ASCII crab mascot to primary documentation entry points.

Changes

• Added ASCII art crab to README.md header
• Added ASCII art crab to docs/llms.txt header
• Added 🦀 emoji to titles in both files

# Crabcode 🦀

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Complements existing crab emoji usage throughout codebase without impacting functionality.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Crabcode needs a crab mascot 🦀</issue_title>
<issue_description>Crabcode is shaping up to be a fast, opinionated, and well-designed workspace manager. One thing it does not currently have is any kind of visual or symbolic identity.

Requesting consideration of a project mascot or lightweight visual identifier. This could live in the README, documentation, release notes, or eventually the CLI. The goal would be to give the project a recognizable anchor without impacting functionality or scope.

This is not blocking and has no technical requirements. It is purely an optional quality-of-life and identity improvement. Given the project name, there may be some obvious directions, but leaving that open is likely best.

Happy to help if this is something you want to explore.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Crabcode needs a crab mascot 🦀 #1

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