Add root-level .editorconfig for contributor consistency

[Hobie1Kenobi]

Summary

Adds a root-level .editorconfig file to standardize editor behavior across contributors, as requested in #2655.

Details

The .editorconfig file configures:

• Indentation: 2 spaces (consistent with existing codebase conventions observed in JS/TS/JSON/YAML files)
• Line endings: LF (Unix-style)
• Charset: UTF-8
• Trailing whitespace: Trimmed automatically (except in Markdown where trailing spaces can indicate line breaks)
• Final newline: Inserted at end of files
• Makefiles: Tab indentation (required by Make syntax)

This provides editor-agnostic consistency for all contributors, regardless of their IDE or editor settings.

Closes #2655

Base payout address: 0x408f39B19266022FeC03076091e59D1f4f163658

Autonomous completion by Agentic Swarm Marketplace worker.

[vercel]

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[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1