astro dev object export panics with 'index out of range' on Airflow 3

[jlaneve]

Description

astro dev object export crashes with a runtime panic when the project is running Airflow 3.

Reproduction

1. Create a new Astro project with an Airflow 3 runtime (e.g., astro dev init --runtime-version 3.1-12)
2. Run astro dev start
3. Run astro dev object export

Expected

The command exports connections, variables, and pools from the running Airflow instance to a YAML settings file.

Actual

The command panics:

Exporting Pool: default_pool
successfully exported pools

successfully exported variables

panic: runtime error: index out of range [1] with length 1

goroutine 1 [running]:
github.com/astronomer/astro-cli/settings.ExportConnections({0x...})
	settings/settings.go:574 +0x768

Root cause

settings.ExportConnections (in settings/settings.go) runs airflow connections list -o yaml inside the container and then parses the output by splitting on the literal string "- conn_id:":

yamlCons := "- conn_id:" + strings.SplitN(plainOut, "- conn_id:", 2)[1]

In Airflow 3, the airflow connections list -o yaml output format has changed and no longer contains "- conn_id:", so strings.SplitN returns a slice of length 1 and indexing [1] panics.

Pools and variables export correctly because they use different code paths.

Suggested fix

Either:

1. Switch ExportConnections / ExportVariables / ExportPools to use the Airflow REST API (similar to Batch import Airflow settings to speed up dev start #2078), or
2. Parse the new Airflow 3 YAML format (and handle both v2 and v3 formats), or
3. At minimum, guard the slice access so it returns a clear error instead of panicking

Note: this is unrelated to #2078 (settings import via REST API). That PR only fixes the import path; the export path still uses the old CLI-based approach.