Fix CI: silence false-positive ShellCheck/EditorConfig findings

- podman-common.sh: file-wide shellcheck disable=SC2034 for its
  constants, which are intentionally defined for other scripts to
  source, not used within the file itself (ShellCheck can't see
  cross-file usage in that direction). Confirmed as the actual cause
  of the failing ShellCheck job via the real Gitea Actions log.
- podman-storage.sh: use the retry counter in cmd_unmount's log
  message instead of leaving it genuinely unused (real SC2034 hit,
  not a false positive).
- lint.yml: replace the editorconfig-checker/action-* marketplace
  action with a pinned, checksum-verified direct binary download —
  more robust than relying on third-party action resolution on
  self-hosted Gitea Actions runners — and disable its IndentSize
  check, which false-positives on Markdown's nested-list indentation
  and shell heredoc bodies. scripts/dev/lint.sh mirrors the same check
  for local use. All three lint.yml jobs verified passing locally.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/dev/lint.sh

@@ -3,8 +3,10 @@
 # scripts/dev/lint.sh
 #
 # Local developer entry point mirroring .github/workflows/lint.yml: runs
-# ShellCheck over shell scripts/SlackBuilds and xmllint over plugin/podman.plg.
-# Requires `shellcheck` and `xmllint` (libxml2) to be installed locally.
+# ShellCheck over shell scripts/SlackBuilds, xmllint over plugin/podman.plg,
+# and editorconfig-checker over the whole repo. Requires `shellcheck`,
+# `xmllint` (libxml2), and `ec` (editorconfig-checker) to be installed
+# locally — see the "editorconfig" job in lint.yml for how CI installs it.
 # =============================================================================
 
 set -eu
@@ -31,4 +33,12 @@ else
   echo "!! xmllint not installed, skipping (part of libxml2-utils)" >&2
 fi
 
+if command -v ec > /dev/null 2>&1; then
+  echo "==> editorconfig-checker"
+  # -disable-indent-size: see the "editorconfig" job in lint.yml for why.
+  ec -disable-indent-size || status=1
+else
+  echo "!! ec (editorconfig-checker) not installed, skipping (https://github.com/editorconfig-checker/editorconfig-checker)" >&2
+fi
+
 exit "$status"