fix(install): silence AWS probe when pi settings.json absent

check_aws_env was warning about missing AWS_PROFILE/AWS_REGION even on
fresh machines with no settings.json yet \u2014 but at that point we don't
know which provider the user will pick, so the warning is noise.
check_pi_settings already tells the user to bootstrap settings.json;
the AWS probe now stays quiet until it has evidence (amazon-bedrock in
settings.json) that AWS creds are actually needed.

install.sh

@@ -327,11 +327,11 @@ check_aws_env() {
 
     # Only warn if settings.json selects amazon-bedrock. If pi uses a
     # non-Bedrock provider (bare anthropic, openai, ...) AWS creds are
-    # irrelevant and this probe would be noise.
-    if [[ -f "$PI_SETTINGS_DEST" ]] \
-       && ! grep -q '"amazon-bedrock"' "$PI_SETTINGS_DEST" 2>/dev/null; then
-        return 0
-    fi
+    # irrelevant and this probe would be noise. If settings.json doesn't
+    # exist yet, check_pi_settings already told the user to bootstrap it
+    # — we can't know which provider they'll pick, so stay quiet here.
+    [[ -f "$PI_SETTINGS_DEST" ]] || return 0
+    grep -q '"amazon-bedrock"' "$PI_SETTINGS_DEST" 2>/dev/null || return 0
 
     if [[ -n "${AWS_PROFILE:-}" && -n "${AWS_REGION:-}" ]]; then
         ok "AWS env present (AWS_PROFILE=$AWS_PROFILE, AWS_REGION=$AWS_REGION)"