Extension YAML Graph backup

These files were removed from tom_vscode_extension when the YAML Graph editor feature was retired from the extension. They are preserved here in case the feature is revived (the yaml_graph_core / yaml_graph_vscode packages themselves remain intact).

Original locations within tom_vscode_extension/:

Backup path	Original path
src/handlers/yamlGraph-handler.ts	src/handlers/yamlGraph-handler.ts
example/graph_samples/*.yaml	example/graph_samples/*.yaml
doc/yaml_graph.md	doc/yaml_graph.md
doc/yaml_graph_architecture_design.md	doc/yaml_graph_architecture_design.md
doc/diagram_editing.md	doc/diagram_editing.md
doc/information/mermaid_diagrams.md	doc/information/mermaid_diagrams.md

What was also removed from the extension (not files, so not backed up here):

• tomAi.yamlGraphEditor custom-editor contribution and the three

yamlValidation schema entries in package.json. - The yaml-graph-core / yaml-graph-vscode file: dependencies in package.json. - The registerYamlGraphEditor export (src/handlers/index.ts) and its call in src/extension.ts. - The GLOB_FLOW / GLOB_STATE / GLOB_ER constants in src/utils/constants.ts. - The yaml_graph_core / yaml_graph_vscode build steps in install_extension.sh / install_extension.ps1. - The yaml-graph exclusions in .vscodeignore.