Add Forgejo Actions runner substrate and status probe

Documents interim coulombcore org runner for forgejo.coulomb.social and
adds make forgejo-runner-status for operator health checks.

tools/forgejo-runner-status.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+set -u
+
+FORGEJO_URL="${FORGEJO_URL:-https://forgejo.coulomb.social}"
+RUNNER_HOST="${RUNNER_HOST:-coulombcore}"
+RUNNER_SSH_USER="${RUNNER_SSH_USER:-}"
+RUNNER_SSH_KEY="${RUNNER_SSH_KEY:-}"
+SSH_CONNECT_TIMEOUT="${SSH_CONNECT_TIMEOUT:-5}"
+
+section() { printf '\n## %s\n' "$1"; }
+have() { command -v "$1" >/dev/null 2>&1; }
+http_code() { curl -sS -m 8 -o /dev/null -w '%{http_code}' "$1" 2>/dev/null || printf 'error'; }
+
+section "Tool availability"
+for tool in curl ssh; do
+  if have "$tool"; then printf 'ok: %s\n' "$tool"; else printf 'missing: %s\n' "$tool"; fi
+done
+
+section "Forgejo endpoint checks"
+if have curl; then
+  printf 'forgejo root: %s\n' "$(http_code "${FORGEJO_URL}/")"
+  printf 'forgejo api version: %s\n' "$(http_code "${FORGEJO_URL}/api/v1/version")"
+  printf 'forgejo registry /v2 (GET): %s\n' "$(curl -sS -m 8 -o /dev/null -w '%{http_code}' -X GET "${FORGEJO_URL}/v2/")"
+else
+  echo "curl missing; skipping endpoint checks"
+fi
+
+section "Runner host probe"
+if have ssh; then
+  ssh_target="${RUNNER_HOST}"
+  if [ -n "${RUNNER_SSH_USER}" ]; then ssh_target="${RUNNER_SSH_USER}@${RUNNER_HOST}"; fi
+  ssh_args=(-o BatchMode=yes -o ConnectTimeout="${SSH_CONNECT_TIMEOUT}")
+  if [ -n "${RUNNER_SSH_KEY}" ]; then ssh_args+=(-i "${RUNNER_SSH_KEY}"); fi
+  ssh "${ssh_args[@]}" "${ssh_target}" '
+    set -u
+    echo "host=$(hostname)"
+    if command -v forgejo-runner >/dev/null 2>&1; then forgejo-runner -v || true; else echo "missing: forgejo-runner"; fi
+    if command -v docker >/dev/null 2>&1; then docker --version || true; else echo "missing: docker"; fi
+    if command -v systemctl >/dev/null 2>&1; then
+      systemctl is-active forgejo-runner 2>/dev/null || true
+    fi
+    if [ -f /var/lib/forgejo-runner/.runner ]; then echo "ok: /var/lib/forgejo-runner/.runner present"; fi
+  '
+else
+  echo "ssh missing; skipping runner host probe"
+fi