fix(gstack): one helper-link tree for every hardcoded path, honest doctor stats

gstack skills hardcode ~/.claude/skills/gstack/<path> for 83 shared assets
(bin, scripts/jargon-list.json, ETHOS.md, */sections, review/specialists,
make-pdf/dist, lib/diagram-render/dist, freeze/bin...) but only bin and
browse/dist were linked: make-pdf and diagram failed on every run, cso and
plan-*-review could not read their sections, the freeze hook exited 127.
lib/gstack-links.sh links every top-level entry except SKILL.md, skips
non-skill dirs holding a nested SKILL.md (browser-skills, openclaw,
node_modules), removes the global symlink gstack ./setup plants and refuses
a destination inside the submodule. link.sh, install-plugins.sh and
update-all.sh all call it (three hand-copied blocks gone).

doctor.sh counted 34 skills (find without -L) and zero chars for block
scalar descriptions; lib/doctor-skills.sh reuses the census parser and
counts through the symlinks. Plugin constants re-based on measured values;
install-plugins.sh notes why frontend-design@claude-plugins-official and
brightdata-plugin@synced stay off and describes security-guidance truthfully.

lib/doctor-skills.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# ============================================================
+# lib/doctor-skills.sh — doctor.sh's skill-catalog stats
+#
+# `skill_catalog_stats <skills_dir>` counts every skill reachable
+# through <skills_dir>/*/SKILL.md (symlinks included — Python's
+# glob.glob follows them, verified: a symlinked skill dir matches the
+# pattern the same as a real one) and sums their description length,
+# reusing lib/skill-routing-census.py's extract_description() (handles
+# a plain scalar AND a `|`/`>` YAML block scalar) instead of doctor.sh's
+# old `grep '^description:' | head -1` (0 chars on every block-scalar
+# description) and its `find -maxdepth 2` skill count (missed
+# symlinked skill dirs without `-L`).
+#
+# Prints "<count> <desc_chars>" on stdout and ALWAYS exits 0 — an
+# absent <skills_dir> naturally globs to nothing (0 0, no error); a
+# python failure also prints "0 0" so doctor.sh (which runs under
+# `set -euo pipefail`) never aborts on this check, PLUS one warn line on
+# stderr so a real failure still shows instead of reading as a healthy
+# empty catalog. The warn goes to stderr explicitly (not just via the
+# caller's own warn() convention) because the caller reads this
+# function's stdout with `read -r … < <(skill_catalog_stats …)` — any
+# extra stdout line would corrupt that capture.
+#
+# No `set -euo pipefail` here (mirrors lib/vendor-skills.sh): a sourced
+# lib must not change the caller's shell options.
+# ============================================================
+
+DOCTOR_SKILLS_LIB_DIR="$(cd -P "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+if ! declare -F warn >/dev/null 2>&1; then
+  YELLOW='\033[1;33m'; NC='\033[0m'
+  warn() { echo -e "${YELLOW}⚠${NC}  $1"; }
+fi
+
+# skill_catalog_stats <skills_dir> — see file header.
+skill_catalog_stats() {
+  local dir="$1" census="$DOCTOR_SKILLS_LIB_DIR/skill-routing-census.py"
+  local out rc
+  out=$(python3 - "$dir" "$census" <<'PY'
+import glob, importlib.util, sys
+
+skills_dir, census_path = sys.argv[1], sys.argv[2]
+spec = importlib.util.spec_from_file_location(
+    "skill_routing_census", census_path)
+module = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(module)
+
+paths = glob.glob(skills_dir + "/*/SKILL.md")
+chars = sum(len(module.extract_description(p) or "") for p in paths)
+print(len(paths), chars)
+PY
+  )
+  rc=$?
+  if [ "$rc" -eq 0 ]; then
+    echo "$out"
+    return 0
+  fi
+  warn "skill_catalog_stats: python failed (rc=$rc) — showing 0 0" >&2
+  echo "0 0"
+  return 0
+}