CAMEL-21975: Add route-diagram command to display Camel route diagrams in terminal

[gnodet]

Warning

Draft / POC — not ready for review. This is an early proof-of-concept exploring terminal-native route diagram rendering. The layout algorithm, text fallback, and terminal graphics integration still need work.

Summary

Add a lightweight camel cmd route-diagram command that renders Camel route diagrams directly in the terminal using JLine 4's graphics protocol support (Kitty/Sixel/iTerm2 inline images). This is a lighter-weight alternative to the Playwright/Hawtio approach in #21534.

Features

• Terminal inline rendering via JLine 4's TerminalGraphicsManager (auto-detects Kitty/iTerm2/Sixel)
• Hawtio-style layout: branching EIPs (choice, multicast, doTry, loadBalance, recipientList) lay children horizontally; sequential nodes stack vertically
• Merge lines showing branch convergence with a center dot
• Color-coded nodes by type: from (green), to (blue), EIP (purple), choice (orange), default (gray)
• Customizable colors via --theme/--colors option or DIAGRAM_COLORS env var, following JLine's LS_COLORS/GREP_COLORS convention
• Built-in presets: dark, light, transparent
• PNG export via --output diagram.png
• Text fallback for terminals without graphics support

Usage

camel cmd route-diagram                              # inline terminal display
camel cmd route-diagram --theme light                # light theme
camel cmd route-diagram --output diagram.png         # save to PNG
camel cmd route-diagram --colors "bg=:from=#ff5722"  # custom colors

Depends on

• Fix JBang metadata generation to detect all commands #22221 (bug fix for JBang metadata generation)

Preview

(see comment below for rendered diagram screenshots)

Test plan

• Builds successfully
• Preview images rendered with complex routes (triple nested choice, split+choice, doTry/doCatch/doFinally, multicast inside choice)
• Manual test with running Camel integration
• CI passes

[gnodet]

Preview — Dark Theme

Preview — Light Theme

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Routes rendered (top to bottom):

1. Triple nested choice — 3 levels of choice/when/otherwise
2. Split with nested choice — split body → choice with 3 branches → continuation
3. doTry/doCatch/doFinally — try/catch/finally with multiple endpoints per branch
4. Choice with multicast inside — multicast nested inside a when branch
5. doTry with split — exception handling wrapping a split
6. Choice with throwException — simple error routing
7. Choice with merge — classic CBR with continuation after merge

Claude Code on behalf of Guillaume Nodet