Port Citrus JBang from Picocli to Aesh

[christophd]

Description

Replace Picocli with Aesh as the CLI framework for the Citrus JBang tool (tools/jbang). This follows the same migration that JBang itself completed, as described in From Picocli to Aesh: How Porting JBang's CLI Made Everything Better.

Motivation

Picocli relies on runtime reflection for command and option discovery, which adds startup overhead — especially under GraalVM native image. Aesh uses compile-time annotation processing to generate command metadata as switch statements, eliminating reflection at startup and classpath scanning.

Key benefits observed in JBang's migration:

• ~5x faster native startup (33ms -> 6ms) and ~2x faster on JDK (228ms -> 109ms)
• Practical tab-completion — fast enough to run per-keypress without perceptible lag
• GraalVM-friendly — no reflection configuration needed for native images
• Zero external dependencies — Aesh relies solely on the JDK
• Alignment with JBang — since Citrus JBang runs on JBang, aligning on the same CLI framework reduces friction

Scope

The tools/jbang module currently uses Picocli 4.7.7 with the following command classes that need porting:

• CitrusJBangMain — root command
• CitrusCommand — abstract base class (Callable<Integer>)
• Init, Inspect, Run, ListTests, Complete — top-level commands
• Agent, AgentStart, AgentRun, AgentStop — agent subcommand group

Migration involves:

1. Replace info.picocli:picocli dependency with Aesh
2. Port @Command / @CommandLine.Option / @CommandLine.Parameters annotations to Aesh equivalents (@CommandDefinition, @Option, @Argument)
3. Replace Callable<Integer> pattern with Aesh's command execution model
4. Port tab-completion support (Complete.java currently uses picocli.AutoComplete)
5. Update CitrusJBang.java JBang script directives (//DEPS)

The connectors/citrus-jbang-connector module does not use Picocli directly and should not require changes.

References

• Aesh: https://aeshell.github.io/
• JBang migration blog post: https://www.jbang.dev/learn/from-picocli-to-sh-how-porting-jbang-s-cli-made-everything-better/