feat: add intuitive command aliases

[brigleb]

Summary

Add more intuitive aliases to commands to improve discoverability. Users often think of different terms than Basecamp's official names.

Proposed Aliases

// cmd/campfire/campfire.go
Aliases: []string{"chat", "cf", "chats"}

// cmd/comment/comment.go  
Aliases: []string{"comments", "comm"}

// cmd/document/document.go
Aliases: []string{"doc", "docs", "documents"}

// cmd/card/card.go
Aliases: []string{"cards", "kanban", "board"}

Rationale

• Users might think "chat" before "campfire"
• "comments" (plural) feels more natural for listing
• "kanban" or "board" is intuitive for card tables
• Shorter aliases (cf, comm) speed up power users

Files to Modify

• cmd/campfire/campfire.go
• cmd/comment/comment.go
• cmd/document/document.go
• cmd/card/card.go

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Extracted from PR #79 discoverability analysis