ci: build, test and publish the image once, then let the release reuse it

Drop the pull_request trigger (the branch push already validates the commit),
drop the second npm run build from the lint job (the image build compiles it),
and build the image on arm64 after the cheap checks pass. The CI publishes it
as inputs-<hash>, so the merge to main only re-tags it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

scripts/plano-imagem.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Uso: scripts/plano-imagem.sh <registro> <repositório>
+# Imprime inputs=, image= e reuse= (para $GITHUB_OUTPUT). O hash cobre só os
+# arquivos que entram no build da imagem, não a documentação nem a configuração
+# de ferramentas. reuse=true quando o registro já tem inputs-<hash>.
+set -euo pipefail
+registry=$1; ns=${2,,}
+
+inputs=$(git ls-tree -r HEAD \
+  | awk -F'\t' '$2 !~ /^(\.gitea|\.github|\.claude|\.superset|docs)\// && $2 !~ /^(README.*|CLAUDE\.md|DESIGN\.md|LICENSE|\.gitignore|CHANGELOG\.md|scripts\/release-notes\.sh)$/' \
+  | sha256sum | cut -c1-16)
+token=$(curl -fsS "https://$registry/v2/token?service=container_registry&scope=repository:$ns:pull" | jq -r .token)
+code=$(curl -s -o /dev/null -w '%{http_code}' -I \
+  -H "Authorization: Bearer $token" \
+  -H 'Accept: application/vnd.oci.image.index.v1+json,application/vnd.docker.distribution.manifest.list.v2+json,application/vnd.oci.image.manifest.v1+json' \
+  "https://$registry/v2/$ns/manifests/inputs-$inputs")
+echo "inputs-$inputs -> HTTP $code" >&2
+reuse=false; [ "$code" = 200 ] && reuse=true
+echo "inputs=$inputs"
+echo "image=$registry/$ns"
+echo "reuse=$reuse"