Proposed changes to create release v0.7.0 of libCellML

[github-actions]

Automated release PR for v0.7.0.

Do not merge this PR, it is only for review and testing.
The release process will deal with it when the release is finalised.

[github-actions]

Unit Tests

✅ CI checks passed successfully.

[github-actions]

Documentation Tests

✅ Documentation checks passed successfully.

{
  "end_to_end_test_repo": "libcellml/end-to-end-test-framework",
  "end_to_end_test_tag": "v0.5.0",
  "end_to_end_test_sha": "78ce433c2cd4081f123fc2e7fe7d89fcaaf351ae",
  "database_repo": "libcellml/libcellml.org-documentation-test-database",
  "database_tag": "v0.4.1",
  "database_sha": "714d3b125d8f6f3f5e0216e105e095ca6a30e7d8",
  "timestamp": "2026-07-09T03:03:26Z",
  "test_summary": {
    "total_failed": 0,
    "libcellml_asides": {
      "passed": 6,
      "failed": 0
    },
    "libcellml_howto": {
      "passed": 16,
      "failed": 0
    },
    "libcellml_runtimecodes": {
      "passed": 1,
      "failed": 0
    },
    "libcellml_tutorials": {
      "passed": 20,
      "failed": 0
    }
  }
}