feat: support frontend deployment to Staging B and C (#3706)

## Summary
- Map Staging B (`-sb`) to frontend canister
`uhh2r-oyaaa-aaaad-agbva-cai`, enabling `./scripts/deploy-pr-to-beta -sb
-fe <PR>`
- Handle canister not yet installed: when `.config` can't be fetched,
fall back to `null` defaults for all fields and prompt the user to
provide values instead of erroring out
- Updated help text to show both backend and frontend canister IDs per
staging environment

## Test plan
- [ ] `./scripts/deploy-pr-to-beta -sb -fe -be <PR>` deploys both ends
to Staging B
- [ ] Frontend args are fetched from the Staging B frontend canister
when available
- [ ] When the canister isn't installed yet, all fields default to
`null` and the user is prompted

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: aterga

scripts/deploy-pr-to-beta

@@ -10,9 +10,9 @@ Usage: $0 [--staging-a|-sa | --staging-b|-sb | --staging-c|-sc | --staging <CANI
 Select which staging canister to upgrade and which end(s) to deploy.
 
 Options:
-  --staging-a, -sa        Use Staging A (fgte5-ciaaa-aaaad-aaatq-cai)
-  --staging-b, -sb        Use Staging B (jqajs-xiaaa-aaaad-aab5q-cai)
-  --staging-c, -sc        Use Staging C (y2aaj-miaaa-aaaad-aacxq-cai)
+  --staging-a, -sa        Use Staging A (backend: fgte5-ciaaa-aaaad-aaatq-cai, frontend: gjxif-ryaaa-aaaad-ae4ka-cai)
+  --staging-b, -sb        Use Staging B (backend: jqajs-xiaaa-aaaad-aab5q-cai, frontend: uhh2r-oyaaa-aaaad-agbva-cai)
+  --staging-c, -sc        Use Staging C (backend: y2aaj-miaaa-aaaad-aacxq-cai, frontend: uag4f-daaaa-aaaad-agbvq-cai)
   --staging <CANISTER_ID> Use the provided canister id
   --end <front|back>      Which end(s) to deploy (can be specified multiple times)
   -fe                     Shortcut for --end front
@@ -125,8 +125,8 @@ if [ "$DEPLOY_FRONT" = false ] && [ "$DEPLOY_BACK" = false ]; then
     exit 1
 fi
 
-if [ "$DEPLOY_FRONT" = true ] && [ "$STAGING_NAME" != "a" ]; then
-    echo "Error: Frontend deployment is not yet supported for Staging B, C, or custom canister IDs. Use --staging-a/-sa for frontend deployment." >&2
+if [ "$DEPLOY_FRONT" = true ] && [ "$STAGING_NAME" != "a" ] && [ "$STAGING_NAME" != "b" ] && [ "$STAGING_NAME" != "c" ]; then
+    echo "Error: Frontend deployment is only supported for Staging A, B, and C. Use --staging-a/-sa, --staging-b/-sb, or --staging-c/-sc." >&2
     exit 1
 fi
 
@@ -137,7 +137,14 @@ cd "$ROOT_DIR"
 REPO="dfinity/internet-identity"
 WORKFLOW_FILE="canister-tests.yml"
 WALLET_CANISTER_ID="cvthj-wyaaa-aaaad-aaaaq-cai"
-FRONTEND_CANISTER_ID="gjxif-ryaaa-aaaad-ae4ka-cai"
+
+# Map staging environment to its frontend canister ID
+case "$STAGING_NAME" in
+    a) FRONTEND_CANISTER_ID="gjxif-ryaaa-aaaad-ae4ka-cai" ;;
+    b) FRONTEND_CANISTER_ID="uhh2r-oyaaa-aaaad-agbva-cai" ;;
+    c) FRONTEND_CANISTER_ID="uag4f-daaaa-aaaad-agbvq-cai" ;;
+    *) FRONTEND_CANISTER_ID="" ;;
+esac
 
 source "$SCRIPTS_DIR/frontend-arg-helpers.bash"
 

scripts/frontend-arg-helpers.bash

@@ -44,17 +44,6 @@ build_frontend_install_arg() {
         echo "  Failed, trying next domain..." >&2
         raw_config=""
     done
-    if [ -z "$raw_config" ]; then
-        echo "Error: Could not fetch config from either $primary_url or $fallback_url" >&2
-        exit 1
-    fi
-
-    echo ""
-    echo "Current frontend config:"
-    echo "$raw_config"
-    echo ""
-    echo "Configure install arguments (press Enter to keep each current value):"
-
     # Parse individual fields from the Candid text output.
     # For multi-line nested values (analytics_config, related_origins), we extract
     # everything from "field = " to the matching closing brace/semicolon.
@@ -82,33 +71,48 @@ build_frontend_install_arg() {
         ' <<< "$config"
     }
 
-    local current_backend_canister_id
-    current_backend_canister_id=$(parse_candid_field "backend_canister_id" "$raw_config")
-    local current_backend_origin
-    current_backend_origin=$(parse_candid_field "backend_origin" "$raw_config")
-    local current_related_origins
-    current_related_origins=$(parse_candid_field "related_origins" "$raw_config")
-    local current_fetch_root_key
-    current_fetch_root_key=$(parse_candid_field "fetch_root_key" "$raw_config")
-    local current_analytics_config
-    current_analytics_config=$(parse_candid_field "analytics_config" "$raw_config")
-    local current_dummy_auth
-    current_dummy_auth=$(parse_candid_field "dummy_auth" "$raw_config")
-    local current_dev_csp
-    current_dev_csp=$(parse_candid_field "dev_csp" "$raw_config")
-
-    # All known fields with their defaults (null for missing fields)
+    # All known fields with their defaults (null for missing/new canisters)
     local -a field_names=(backend_canister_id backend_origin related_origins fetch_root_key analytics_config dummy_auth dev_csp)
     local -A current_values=(
-        [backend_canister_id]="$current_backend_canister_id"
-        [backend_origin]="$current_backend_origin"
-        [related_origins]="$current_related_origins"
-        [fetch_root_key]="$current_fetch_root_key"
-        [analytics_config]="$current_analytics_config"
-        [dummy_auth]="$current_dummy_auth"
-        [dev_csp]="$current_dev_csp"
+        [backend_canister_id]="null"
+        [backend_origin]="null"
+        [related_origins]="null"
+        [fetch_root_key]="null"
+        [analytics_config]="null"
+        [dummy_auth]="null"
+        [dev_csp]="null"
     )
 
+    if [ -z "$raw_config" ]; then
+        echo "" >&2
+        echo "Warning: Could not fetch config from:" >&2
+        echo "  - $primary_url" >&2
+        echo "  - $fallback_url" >&2
+        echo "The canister may not be installed yet, or there may be a network issue." >&2
+        echo "All fields will default to null. Please provide values for each field." >&2
+        read -r -p "Continue with null defaults? [Y/n]: " confirm </dev/tty >&2
+        if [[ "$confirm" =~ ^[Nn] ]]; then
+            echo "Aborted by user." >&2
+            exit 1
+        fi
+    else
+        echo ""
+        echo "Current frontend config:"
+        echo "$raw_config"
+
+        # Parse current values from the fetched config
+        for field in "${field_names[@]}"; do
+            local parsed
+            parsed=$(parse_candid_field "$field" "$raw_config")
+            if [ -n "$parsed" ]; then
+                current_values[$field]="$parsed"
+            fi
+        done
+    fi
+
+    echo ""
+    echo "Configure install arguments (press Enter to keep each current value):"
+
     # Prompt for each field, defaulting empty values to null
     local -A final_values
     for field in "${field_names[@]}"; do