feat: add -c/--command option to specify container command

[nihen]

Summary

• Add -c/--command option to specify the command to execute inside the container
• Also configurable via ECSSH_COMMAND environment variable
• Default remains /bin/bash when not specified

Usage

ecssh -c "ls -la" my-cluster web-app           # Run a one-liner command
ecssh -c "/bin/sh" my-cluster web-app          # Connect with sh
ECSSH_COMMAND="whoami" ecssh my-cluster web-app # Specify via env var

Test plan

• Verify command execution with -c "ls -la"
• Verify /bin/bash is used by default without -c
• Verify ECSSH_COMMAND environment variable works
• Verify -c option takes priority over ECSSH_COMMAND
• Verify ecssh help shows the -c option

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds support for specifying the command executed inside the ECS container via a new CLI option and an environment variable, while keeping /bin/bash as the default.

Changes:

• Extend container connection flow to accept a user-provided command (defaulting to /bin/bash when empty).
• Add -c/--command CLI parsing and ECSSH_COMMAND environment variable support.
• Update usage/help text and Claude guidance examples to document the new option.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
main.go	Plumbs a command parameter through connection logic, adds -c/--command parsing, reads ECSSH_COMMAND, and updates usage output.
CLAUDE.md	Documents examples for -c and ECSSH_COMMAND.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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