feat(resolver,graph): fetch and resolve include: remote: HTTPS URLs

Remote includes (include: remote: https://...) were previously skipped
silently in the resolver and rendered as unexpanded leaf nodes in the
graph.

Changes:
- fetcher.FetchURL: new shared unauthenticated HTTP GET helper
- resolver: resolveRemoteInclude fetches the URL, parses YAML, sets job
  origin to the URL string, recursively resolves sub-includes, and emits
  a warning on failure (lint continues on the rest of the pipeline)
- graph: recurseRemote fetches the URL, captures direct job names, and
  recurses into sub-includes so remote nodes expand like local ones

Adds testdata/includes_remote.yml fixture.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/graph/includes.go

@@ -114,7 +114,9 @@ func (b *treeBuilder) parseMap(m map[string]any) []*treeNode {
 		return []*treeNode{node}
 	}
 	if remote, ok := m["remote"].(string); ok {
-		return []*treeNode{{id: b.nextID(), label: "remote:<br>" + mermaidLabel(remote), class: "remote"}}
+		node := &treeNode{id: b.nextID(), label: "remote:<br>" + mermaidLabel(remote), class: "remote"}
+		b.recurseRemote(node, remote)
+		return []*treeNode{node}
 	}
 	if tmpl, ok := m["template"].(string); ok {
 		return []*treeNode{{id: b.nextID(), label: "template:<br>" + mermaidLabel(tmpl), class: "template"}}
@@ -170,6 +172,28 @@ func (b *treeBuilder) recurseProject(node *treeNode, project, filePath, ref stri
 	b.buildChildren(node, p.Include)
 }
 
+func (b *treeBuilder) recurseRemote(node *treeNode, rawURL string) {
+	key := "remote:" + rawURL
+	if b.visited[key] {
+		return
+	}
+	b.visited[key] = true
+
+	data, err := fetcher.FetchURL(rawURL)
+	if err != nil {
+		return
+	}
+	p, err := model.ParseBytes(data)
+	if err != nil {
+		return
+	}
+	node.jobs = jobNames(p)
+	if len(p.Include) == 0 {
+		return
+	}
+	b.buildChildren(node, p.Include)
+}
+
 func (b *treeBuilder) recurseComponent(node *treeNode, ref string) {
 	if strings.ContainsRune(ref, '$') {
 		return