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>

Taskfile.yml

@@ -41,6 +41,8 @@ tasks:
         ignore_error: true
       - cmd: ./{{.BINARY}} check testdata/keywords_invalid.yml
         ignore_error: true
+      - cmd: ./{{.BINARY}} check testdata/includes_remote.yml
+        ignore_error: false
       - cmd: ./{{.BINARY}} check testdata/includes_project.yml
         ignore_error: false
       - cmd: ./{{.BINARY}} check testdata/includes_component.yml