[EXT] `extensionList` output lacks chalk formatting (inconsistent with other commands)

[flyingrobots]

Problem

git mind extension list outputs plain text (e.g., roadmap 1.0.0 [builtin]) while every other command uses the chalk-based format helpers from src/cli/format.js for colored, structured output.

commands.js doesn't import chalk directly (all color goes through format.js), so the extension list command had to drop the formatting.

Work

• Add formatExtensionList(extensions) to src/cli/format.js
• Update extensionList() in src/cli/commands.js to call it
• Use chalk for extension name (bold), version (dim), builtin tag (dim vs cyan), description (dim), views/lenses lists

Ref: #252

[flyingrobots]

Resolved in ae72cd2 (PR #270)