feat: add interactive TUI and abstract display output for OAuth flows

[appleboy]

• Add a new TUI interface using BubbleTea and Lipgloss for interactive terminal OAuth flows
• Refactor all CLI output to use a Displayer abstraction
• Support both TUI and plain text output based on terminal detection
• Replace direct stdout printing with Displayer calls throughout the OAuth logic
• Implement device flow progress, token info, and error handling visually in the TUI
• Integrate new Displayer implementations (TUI, plain, test/noop) and message types
• Update tests to use NoopDisplayer for refresh and polling flows
• Add BubbleTea, Lipgloss, and Charm libraries to dependencies
• Improve UX with status logs, spinners, and styled banners for each OAuth phase

[Copilot]

Pull request overview

This PR introduces a terminal UI (BubbleTea/Lipgloss) for interactive OAuth device flows and refactors OAuth-related CLI output behind a Displayer abstraction to support both TUI and plain-text output depending on terminal detection.

Changes:

• Added a new tui package (model + message types) and Displayer implementations (TUI program sender, plain text, noop for tests).
• Refactored the OAuth flow in main.go to emit output exclusively via tui.Displayer and to select TUI vs plain mode at runtime.
• Updated tests to pass a NoopDisplayer into refactored functions.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tui/model.go	BubbleTea model rendering OAuth device flow phases and status log.
tui/messages.go	Message types sent from OAuth logic to the TUI model.
tui/displayer.go	Displayer interface + Plain/Program/Noop implementations.
main.go	Refactors flow to use Displayer; adds TUI bootstrapping and terminal detection.
polling_test.go	Updates polling tests for new pollForTokenWithProgress(..., Displayer) signature.
main_test.go	Updates refresh token tests for new refreshAccessToken(..., Displayer) signature.
go.mod / go.sum	Adds Charm/BubbleTea/Lipgloss dependencies and indirect transitive deps.

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