chore(actions/setup): add diagnostic ls when external-tools.json lookup fails

Every fleet repo's CI has been failing for >24h with
"socket-registry setup action is broken: external-tools.json
not found at ${GITHUB_ACTION_PATH}/../../../external-tools.json".

The file exists in this repo at every relevant SHA — locally
the path resolves correctly. The runner-side failure is
either (a) the action checkout is sparse and excludes the
repo-root file, or (b) GITHUB_ACTION_PATH isn't where we
expect on the GitHub runner.

Drop in a series of `ls -la` calls on the action path and
its three ancestor directories when the lookup fails, so the
next failing run shows what's actually present and we can
fix the path math (or the action packaging) accordingly.
Diagnostic-only: the failure path still exits 1 with the
original error message preserved up top.

Pre-commit lint/test bypassed via DISABLE_PRECOMMIT_* — local
SOCKET_API_KEY 401s the sfw pnpm shim. User-authorized via
'Allow lint bypass' / 'Allow no-verify bypass' earlier in
this session.

Author: jdalton

.github/actions/setup/action.yml

@@ -52,6 +52,17 @@ runs:
         if [ ! -f "$TOOLS_FILE" ]; then
           echo "× socket-registry setup action is broken: external-tools.json not found at ${TOOLS_FILE}." >&2
           echo "  This is a packaging bug in SocketDev/socket-registry, not a consumer issue. File a bug." >&2
+          echo "" >&2
+          echo "  Diagnostics — what's actually present at runtime:" >&2
+          echo "    GITHUB_ACTION_PATH=${GITHUB_ACTION_PATH}" >&2
+          echo "    ls -la \"\${GITHUB_ACTION_PATH}\":" >&2
+          ls -la "${GITHUB_ACTION_PATH}" 2>&1 | sed 's/^/      /' >&2 || true
+          echo "    ls -la \"\${GITHUB_ACTION_PATH}/..\" (parent — should be .github/actions/):" >&2
+          ls -la "${GITHUB_ACTION_PATH}/.." 2>&1 | sed 's/^/      /' >&2 || true
+          echo "    ls -la \"\${GITHUB_ACTION_PATH}/../..\" (grandparent — should be .github/):" >&2
+          ls -la "${GITHUB_ACTION_PATH}/../.." 2>&1 | sed 's/^/      /' >&2 || true
+          echo "    ls -la \"\${GITHUB_ACTION_PATH}/../../..\" (great-grandparent — should be repo root):" >&2
+          ls -la "${GITHUB_ACTION_PATH}/../../.." 2>&1 | sed 's/^/      /' >&2 || true
           exit 1
         fi
         # Copy the tools file to RUNNER_TEMP so consumer workflows and