fix(install): honor comma-separated --tool list (as the help documents) (#678)

The help text advertised `--tool <a,b>` (a comma list), but --tool took a
single value and validated it whole, so `--tool claude-code,cursor` failed
with "Unknown tool 'claude-code,cursor'". --division and --agent already
split on commas; --tool didn't (#671).

Split --tool on commas, trim each entry, and validate each against
ALL_TOOLS (mirrors --division), so a bad entry still errors clearly by
name. Single-tool use is unchanged.

Verified: --tool claude-code,cursor installs both; "claude-code, cursor"
(with spaces) works; --tool claude-code,nope errors on 'nope'; --tool
cursor still works.

Fixes #671


Claude-Session: https://claude.ai/code/session_01WKnDRWM4izsB8WAXKszhsq

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

scripts/install.sh

@@ -1183,14 +1183,21 @@ main() {
 
   check_integrations
 
-  # Validate explicit tool
+  # Validate explicit tool(s). --tool accepts a comma-separated list (like
+  # --division / --agent), e.g. --tool claude-code,cursor.
+  local _tool_list=()
   if [[ "$tool" != "all" ]]; then
-    local valid=false t
-    for t in "${ALL_TOOLS[@]}"; do [[ "$t" == "$tool" ]] && valid=true && break; done
-    if ! $valid; then
-      err "Unknown tool '$tool'. Valid: ${ALL_TOOLS[*]}"
-      exit 1
-    fi
+    local _t
+    IFS=',' read -ra _tool_list <<< "$tool"
+    local _cleaned=()
+    for _t in "${_tool_list[@]}"; do
+      _t="$(printf '%s' "$_t" | xargs)"; [[ -z "$_t" ]] && continue
+      local valid=false _vt
+      for _vt in "${ALL_TOOLS[@]}"; do [[ "$_vt" == "$_t" ]] && valid=true && break; done
+      $valid || { err "Unknown tool '$_t'. Valid: ${ALL_TOOLS[*]}"; exit 1; }
+      _cleaned+=("$_t")
+    done
+    _tool_list=("${_cleaned[@]}")
   fi
 
   # Decide whether to show interactive UI
@@ -1207,7 +1214,7 @@ main() {
     : # wizard committed SELECTED_TOOLS + FILTER_DIVISIONS
 
   elif [[ "$tool" != "all" ]]; then
-    SELECTED_TOOLS=("$tool")
+    SELECTED_TOOLS=("${_tool_list[@]}")
 
   else
     # Non-interactive (or no TTY): auto-detect