Add logging infrastructure without subshell overhead

Add optional logging to file via PROXDOC_LOGFILE environment
variable. Uses exec redirection with tee instead of subshells,
which is more efficient for long-running diagnostics.

Usage: PROXDOC_LOGFILE=/tmp/proxdoc.log ./proxDoc.sh --diags

#9

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

proxDoc.sh

@@ -7,6 +7,12 @@ VERSION="1.1.0"
 ###################
 readonly CMD_TIMEOUT=30  # Default timeout in seconds for external commands
 
+###################
+# Logging Configuration
+###################
+# Optional log file - set via environment variable PROXDOC_LOGFILE
+LOGFILE="${PROXDOC_LOGFILE:-}"
+
 ###################
 # Pattern Constants
 ###################
@@ -705,7 +711,28 @@ help() {
 ###################
 # Main Functions
 ###################
+
+# Setup logging if LOGFILE is specified
+setup_logging() {
+    if [[ -n "$LOGFILE" ]]; then
+        # Create log directory if needed
+        local log_dir
+        log_dir=$(dirname "$LOGFILE")
+        if [[ ! -d "$log_dir" ]]; then
+            mkdir -p "$log_dir" 2>/dev/null || {
+                log_message warn "Cannot create log directory: $log_dir"
+                LOGFILE=""
+                return
+            }
+        fi
+        log_message info "Logging output to: $LOGFILE"
+        # Redirect stdout and stderr to tee (no subshell overhead)
+        exec > >(tee -a "$LOGFILE") 2>&1
+    fi
+}
+
 runDiags() {
+    setup_logging
     log_message info "Beginning system examination..."
     
     # Check if running on Proxmox