Plain mode: support port forwarding

[Horiodino]

Fixes #2962

Changes

• Added --port-forward CLI flag to limactl create, allowing users to specify static port forwards even in plain mode.
• Modified host agent to set up static SSH-based TCP port forwarding in plain mode.
• Updated YAML expressions to handle portForwards from CLI.
• Added validation warnings for large port ranges in plain mode.

[nirs]

It is not clear what is the suggested behavior. Can we start with the documentation instead of the code, so we have clear understanding of wanted behavior?

[nirs]

We should also test mixed ports. Both dynamic and static ports will be available when running in normal mode, but only the static ports will be available in --plain mode.

I'm not sure if static ports should be served using ssh when running in normal mode, but this is implementation detail.

[Copilot]

Pull Request Overview

Adds support for user-defined static port forwarding in plain mode by extending the CLI, YAML schema, host agent logic, and validation.

• Introduce a --port-forward flag with parsing and YQ expression generation
• Extend PortForward with Static, filter non-static rules in plain mode, and warn on large port ranges
• Update host agent to separate/apply static forwards and add end-to-end tests + CI jobs

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/portfwd/forward.go	Skip dynamic forwarding for statically handled ports
pkg/limayaml/validate.go	Warn for port ranges >10 in plain mode
pkg/limayaml/limayaml.go	Add Static field to PortForward struct
pkg/limayaml/defaults.go	Remove non-static forwards when plain mode is enabled
pkg/limayaml/defaults_test.go	Tests for filtering static vs. non-static forwards
pkg/hostagent/hostagent.go	Separate and apply static forwards; adjust event loop logic
cmd/limactl/editflags/editflags.go	Register port-forward flag and implement parsing & expression
cmd/limactl/editflags/editflags_test.go	Unit tests for ParsePortForward and BuildPortForwardExpression
hack/test-templates/static-port-forward.yaml	Template covering static/dynamic port examples
hack/test-plain-static-port-forward.sh	Script to verify static-only forwarding in plain mode
hack/test-nonplain-static-port-forward.sh	Script to verify full forwarding in normal mode
.github/workflows/test.yml	CI jobs to run the new static port forwarding tests

Comments suppressed due to low confidence (2)

pkg/hostagent/hostagent.go:619

• [nitpick] Consider adding unit or integration tests for separateStaticPortForwards and addStaticPortForwardsFromList to verify correct separation and application of static port-forwarding rules.

func (a *HostAgent) addStaticPortForwardsFromList(ctx context.Context, staticPortForwards []limayaml.PortForward) {

pkg/hostagent/hostagent.go:642

• The loop uses for i := range len(a.instConfig.PortForwards), which attempts to range over an int and will not compile. Change it to for i := range a.instConfig.PortForwards or use a classic indexed loop like for i := 0; i < len(...); i++.

	for i := range len(a.instConfig.PortForwards) {