[FEATURE]: Template-generated specs should fall back to templates/dml and templates/schemas

[rederik76]

Is there an existing issue for this?

• I have searched the existing issues

Problem statement

functionPath on template-generated specs already searches the instantiating dataflow, then templates/python_functions/. Relative sqlPath and schemaPath do not.

Those values are always resolved under the dataflow group (…/dataflowspec/<subdir>/ then …/<subdir>/). Shared files next to a template (src/templates/dml/…, src/templates/schemas/…) are never considered, so template authors cannot reuse SQL or schemas the way they reuse Python functions.

Regular (non-template) specs should keep resolving DML and schemas only next to the spec. Extra fallbacks are not needed there.

Proposed Solution

For specs tagged _isTemplateGenerated, resolve relative paths in this order:

sqlPath

1. DML next to the spec (same as today: dataflow group dml/)
2. DML under the bundle templates directory (templates/dml/<file>)

schemaPath

1. Schemas next to the spec (same as today: dataflow group schemas/)
2. Schemas under the bundle templates directory (templates/schemas/<file>)

If a file is found, use that absolute path. Regular specs must not search templates/dml/ or templates/schemas/.

Mirror the existing functionPath pattern in dataflow_spec_builder.py, add unit tests for both spec kinds, and document the search order next to the Python function fallback in the templates docs.

Additional Context

• LOCALISE_PATHS already maps sqlPath → ./dml and schemaPath → ./schemas.
• _isTemplateGenerated is set in template_processor.py.
• Analogous Python search: bundle/templates/python_functions/<file> for generated specs only.
• sqlPath fallback is implemented in feat: fall back to templates/dml and templates/schemas for generated specs #151. schemaPath is still missing.