feat(ralphex-dk): add --image and --port CLI flags

[umputun]

Mirror the existing RALPHEX_IMAGE and RALPHEX_PORT env vars with CLI flags, consistent with how --docker, --network, and --claude-provider expose their env-backed settings. CLI flags take precedence over env vars when both are set.

Related to #298

[Copilot]

Pull request overview

This PR adds --image and --port CLI flags to the ralphex-dk Docker wrapper so users can set the Docker image and dashboard port without relying on RALPHEX_IMAGE / RALPHEX_PORT, with CLI taking precedence over environment variables.

Changes:

• Add --image / --port wrapper flags and resolve their values with CLI > env > default precedence.
• Add unit tests covering parsing and precedence behavior for image/port resolution in main().
• Update README and llms.txt to document the new flag equivalents for the existing env vars.

Reviewed changes

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

File	Description
scripts/ralphex-dk/ralphex_dk_test.py	Adds tests for --image/--port parsing and for CLI/env/default resolution in main().
scripts/ralphex-dk.sh	Introduces the new argparse flags and uses them when resolving the wrapper’s image/port settings.
llms.txt	Documents --image and --port as CLI counterparts to RALPHEX_IMAGE / RALPHEX_PORT.
README.md	Updates Docker wrapper env var docs to reference the new CLI flags.

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[Copilot]

--port here only changes the host-side docker -p mapping, but ralphex inside the container still runs with its own --port default (8080). This can make ralphex print a URL with the wrong port when --port/RALPHEX_PORT is set. Consider passing the chosen port through to ralphex (and mapping host:port to container:port) or, at minimum, clarifying in the flag help that it’s a host bind port remap to container 8080.

[Copilot]

Using parsed.image or ... / parsed.port or ... makes precedence depend on truthiness, not whether the flag was provided. If a user passes an empty string (e.g. --image ''), the env var would incorrectly win even though the CLI flag was set. Prefer explicit is not None checks for these optional argparse values to guarantee "CLI overrides env" semantics.

Suggested change

	image = parsed.image or os.environ.get("RALPHEX_IMAGE", DEFAULT_IMAGE)
	port = parsed.port or os.environ.get("RALPHEX_PORT", DEFAULT_PORT)
	network = parsed.network or os.environ.get("RALPHEX_DOCKER_NETWORK", "")
	image = parsed.image if parsed.image is not None else os.environ.get("RALPHEX_IMAGE", DEFAULT_IMAGE)
	port = parsed.port if parsed.port is not None else os.environ.get("RALPHEX_PORT", DEFAULT_PORT)
	network = parsed.network if parsed.network is not None else os.environ.get("RALPHEX_DOCKER_NETWORK", "")