fix(installer): clearer pnpm/corepack errors + dev-aware --check

Review follow-ups on the --dev feature:
- Pin corepack to pnpm@10.6.2 (the repo packageManager) and surface
  corepack enable/prepare failures, with an actionable hard-fail when pnpm
  is still absent — the fresh-machine path no longer dies on a bare
  "command not found".
- `--check --dev` now reports the installed version instead of a
  misleading "Could not reach registry" warning (dev mode skips the
  registry lookup).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RMoEx7hfdFGjUiCHuN1RRi

tools/install.sh

@@ -305,13 +305,21 @@ install_cli_from_source() {
   local out_dir="$WORK_DIR/dist-tarballs"
   mkdir -p "$out_dir"
 
-  # pnpm via corepack (ships with Node >= 16.9; required by Node >= 20 preflight)
+  # pnpm via corepack (ships with Node >= 16.9; required by Node >= 20 preflight).
+  # Pin to the repo's packageManager version so the build matches CI. Surface
+  # corepack failures so the fresh-machine case gives an actionable error
+  # instead of a bare "command not found".
   if ! command -v pnpm &>/dev/null; then
     info "Activating pnpm via corepack…"
-    corepack enable >/dev/null 2>&1 || true
+    corepack enable 2>&1 | sed 's/^/  /' || warn "corepack enable failed — pnpm may need manual install."
-    corepack prepare pnpm@latest --activate >/dev/null 2>&1 || true
+    corepack prepare pnpm@10.6.2 --activate 2>&1 | sed 's/^/  /' \
+      || warn "corepack prepare failed — pnpm may need manual install."
+  fi
+  if ! command -v pnpm &>/dev/null; then
+    fail "pnpm not available after corepack activation."
+    echo "  Install pnpm manually (https://pnpm.io/installation) and re-run with --dev."
+    exit 1
   fi
-  require_cmd pnpm
 
   info "Installing workspace dependencies (pnpm install)…"
   ( cd "$src" && pnpm install ) 2>&1 | sed 's/^/  /'
@@ -469,7 +477,9 @@ if [[ "$FLAG_CLI" == "true" ]]; then
   echo ""
 
   if [[ "$FLAG_CHECK" == "true" ]]; then
-    if [[ -z "$LATEST" ]]; then
+    if [[ "$FLAG_DEV" == "true" ]]; then
+      info "Dev mode: installed version is ${CURRENT:-(none)} (no registry comparison)."
+    elif [[ -z "$LATEST" ]]; then
       warn "Could not reach registry."
     elif [[ -z "$CURRENT" ]]; then
       warn "Not installed."