G6: analytics averages quoted duration_s values (#1728)

gstack-skill-end writes duration_s as a quoted string, and the per-skill
average stripped everything from the leading quote, so every average
read 0s. The awk now drops a leading quote before extracting digits.

Co-authored-by: Ryan Alberts <ryan.a.alberts@gmail.com>

bin/gstack-analytics

@@ -170,7 +170,9 @@ echo "$SKILL_COUNTS" | while read -r COUNT SKILL; do
       # Extract duration_s value using split on "duration_s":
       n = split($0, parts, "\"duration_s\":")
       if (n >= 2) {
-        # parts[2] starts with the value, e.g. "142,"
+        # parts[2] starts with the value: unquoted (142,...) or quoted ("142",...),
+        # which gstack-skill-end writes. Strip a leading quote before the digits.
+        sub(/^"/, "", parts[2])
         gsub(/[^0-9.].*/, "", parts[2])
         if (parts[2]+0 > 0) { total += parts[2]; count++ }
       }