feat(gstack): share the Playwright bump, report the browser cache

Extract gstack_bump_playwright_if_unsupported from install-plugins.sh into
lib/gstack-playwright.sh and call it from update-all.sh too. A submodule
update no longer leaves the OS-support bump unapplied until the next
`make plugin` — that was BDR-029's open caveat.

The update helper never touches the submodule working tree: on failure it
prints git's own message and points at `make plugin`, and returns non-zero
so the existing `else warn` arm still handles it.

Add a read-only `Playwright browsers` section to doctor.sh: cache size,
which registered install requires each revision, and counts of unreferenced
directories and broken links. No pruning is written — Playwright's own
`install` already unions the required set across every registered install,
and all three installs here are live (rev 1228 for gstack + gsd-pi 1.61,
rev 1243 for gsd-pi 1.63).

Carries two latent-bug fixes from the moved code: the ostag capture exited
1 on every non-Ubuntu host and aborted the caller under inherited errexit,
and the bun calls had no timeout.

install-plugins.sh

@@ -26,8 +26,10 @@ else
 fi
 
 # Load shared detection library
-# shellcheck source=lib/detect-plugins.sh
+# shellcheck source=lib/detect-plugins.sh disable=SC1091
 source "$REPO/lib/detect-plugins.sh"
+# shellcheck source=lib/gstack-playwright.sh disable=SC1091
+source "$REPO/lib/gstack-playwright.sh"
 
 # ── Guard hand-curated config against installer drift ────────
 # graphify's installer (Step 7) rewrites CLAUDE.md + .claude/settings.json
@@ -291,35 +293,6 @@ fi
 
 echo ""
 
-# gstack pins Playwright (1.58.x) which only ships browser builds for
-# ubuntu<=24.04. On a newer distro the browser install fails ("does not
-# support chromium on ubuntuXX.04"). Bump gstack's Playwright to a version
-# that supports this OS so ./setup builds the browse binary against it and
-# installs a native browser. Fires only when the pinned version genuinely
-# lacks support — idempotent across runs. Edits the submodule locally (goes
-# dirty); a `git submodule update` resets it and the next install re-applies.
-# See BLK-008 / LRN-040.
-gstack_bump_playwright_if_unsupported() {
-  [ -d "$GSTACK_DIR" ] && [ -r /etc/os-release ] || return 0
-  local ostag pwlib
-  # shellcheck disable=SC1091
-  ostag="$(. /etc/os-release 2>/dev/null; [ "${ID:-}" = ubuntu ] && printf 'ubuntu%s' "${VERSION_ID:-}")"
-  [ -n "$ostag" ] || return 0   # only the known Ubuntu case
-  pwlib="$GSTACK_DIR/node_modules/playwright-core/lib"
-  # populate node_modules at the pinned version so we can read its support list
-  ( cd "$GSTACK_DIR" && { bun install --frozen-lockfile >/dev/null 2>&1 || bun install >/dev/null 2>&1; } ) || return 0
-  if grep -rqs "$ostag" "$pwlib" 2>/dev/null; then
-    return 0   # pinned Playwright already supports this OS
-  fi
-  info "gstack's Playwright lacks $ostag support — bumping to latest (local submodule edit)..."
-  ( cd "$GSTACK_DIR" && bun add playwright@latest >/dev/null 2>&1 )
-  if grep -rqs "$ostag" "$pwlib" 2>/dev/null; then
-    ok "gstack Playwright bumped — now supports $ostag (browse binary rebuilt by ./setup)"
-  else
-    warn "Playwright bump didn't add $ostag support — gstack browser may stay unavailable"
-  fi
-}
-
 # ============================================================
 # STEP 2 — GSTACK SUBMODULE
 # ============================================================
@@ -367,7 +340,8 @@ if [ -d "$GSTACK_DIR" ]; then
   # BEFORE ./setup so its frozen-lockfile install picks up the new version and
   # the browse binary is rebuilt against it (avoids the "does not support
   # chromium" fail). Non-fatal if it can't — gstack is OFF by default.
-  gstack_bump_playwright_if_unsupported
+  # See BLK-008 / LRN-040 / BDR-029; logic lives in lib/gstack-playwright.sh.
+  gstack_bump_playwright_if_unsupported "$GSTACK_DIR"
 
   info "Running GStack setup..."
   _gstack_setup_ok=0