[DHAKED440]

Fixes #733

Problem

add_nodes and add_edges could increase num_nodes without extending graph_indicator, leaving batched graphs inconsistent and causing downstream operations to misbehave or fail.

Solution

Reject node growth on batched graphs until the API defines which component graph should own new nodes. Preserve unbatched behavior and extend an explicit indicator for single-graph inputs.

Changes

• Guard ambiguous node growth in add_nodes and add_edges.
• Update the function documentation and GNNGraphs development version.
• Add regression coverage for batched growth, valid existing-node edge additions, single-graph indicators, unbatched graphs, and no-op cases.

Testing

• Reproduced the original inconsistency before the fix.
• Pkg.test("GNNGraphs"; coverage=false): 1,391 passed, 8 broken, 1,399 total; the test runner reported success.
• git diff --check: passed.