refactor(e2e): normalize unused-arg comments in headless_env functions (#3113)

GCP, Sprite, and DigitalOcean had commented-out code `# local agent="$2"`
in their `_headless_env` functions. Hetzner already used the cleaner style
`# $2 = agent (unused but part of the interface)`. Normalize to match.

Co-authored-by: spawn-qa-bot <qa@openrouter.ai>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 3 people

sh/e2e/lib/clouds/digitalocean.sh

@@ -73,7 +73,7 @@ _digitalocean_validate_env() {
 # ---------------------------------------------------------------------------
 _digitalocean_headless_env() {
   local app="$1"
-  # local agent="$2"  # unused but part of the interface
+  # $2 = agent (unused but part of the interface)
 
   printf 'export DO_DROPLET_NAME="%s"\n' "${app}"
   printf 'export DO_DROPLET_SIZE="%s"\n' "${DO_DROPLET_SIZE:-${_DO_DEFAULT_SIZE}}"

sh/e2e/lib/clouds/gcp.sh

@@ -92,7 +92,7 @@ process.stdout.write(d.GCP_ZONE || '');
 # ---------------------------------------------------------------------------
 _gcp_headless_env() {
   local app="$1"
-  # local agent="$2"  # unused but part of the interface
+  # $2 = agent (unused but part of the interface)
 
   printf 'export GCP_INSTANCE_NAME="%s"\n' "${app}"
   printf 'export GCP_PROJECT="%s"\n' "${GCP_PROJECT:-}"

sh/e2e/lib/clouds/sprite.sh

@@ -129,7 +129,7 @@ _sprite_validate_env() {
 # ---------------------------------------------------------------------------
 _sprite_headless_env() {
   local app="$1"
-  # local agent="$2"  # unused but part of the interface
+  # $2 = agent (unused but part of the interface)
 
   printf 'export SPRITE_NAME="%s"\n' "${app}"
   if [ -n "${_SPRITE_ORG}" ]; then