feat(gen-shacl): generate sh:sparql constraints from LinkML rules

[jdsika]

Summary

Implement SHACL-SPARQL constraint generation for the boolean-guard pattern commonly used in conditional validation rules. When a LinkML class has
ules:\ blocks with preconditions (\�alue_presence: PRESENT) and postconditions (^[quals_string: true), the generator now emits \sh:SPARQLConstraint\ nodes on the corresponding \sh:NodeShape.

Features

• New _add_rules()\ method translates recognised rule patterns to SPARQL
• Boolean-guard pattern: if value present then flag must be true
• Rule \description\ mapped to \sh:message\ on the constraint
• Deactivated rules are skipped
• Warnings emitted for \�idirectional/\open_world\ rule flags
• New --emit-rules/--no-emit-rules\ CLI flag (default: enabled)
• Full URI references in SPARQL (no PREFIX declarations needed)

Standards Compliance

• W3C SHACL Section 5 (SPARQL-based Constraints)
• Pre-bound \\ variable per Section 5.3.1
• Validated by pyshacl with ^Gdvanced=True\

How was this tested?

• 8 new tests in \ est_shaclgen.py\ covering:
  • Boolean-guard pattern generation
  • \sh:message\ from rule description
  • Correct slot URI resolution
  • Deactivated rule skipping
  • Unsupported pattern handling
  • --no-emit-rules\ suppression
  • No-rules class (no-op)
  • Multiple rules per class

Related issues and stack

Refs: linkml#2464

This PR is the base of a stacked series: #19 (presence-implies-value) → #20 (compositional fallback M1–M5) → #21 (hardening) → #22 (audit fixes). Integration branch: #18.

Areas of uncertainty

• Only the named rule patterns are translated here; combinations outside them are skipped. The pattern set is extended and hardened by the stacked PRs feat(gen-shacl): add presence-implies-value rule pattern (stacked on #11) #19 (presence-implies-value), feat(gen-shacl): add compositional fallback rule converters (M1-M5) #20 (compositional fallback), fix(gen-shacl): correct rule-converter path parity, combined bounds, and SPARQL escaping #21 (hardening) and fix(gen-shacl): enforce operator exactness, nested-slot parity, numeric bounds #22 (audit fixes). When upstreaming, fold the fix(gen-shacl): correct rule-converter path parity, combined bounds, and SPARQL escaping #21/fix(gen-shacl): enforce operator exactness, nested-slot parity, numeric bounds #22 fixes that touch code introduced here (induced-slot parity, SPARQL string escaping, operator exactness) into this submission.
• The boolean guard compares ?flag != true (xsd:boolean); flags modeled as strings dispatch to presence-implies-value only from fix(gen-shacl): enforce operator exactness, nested-slot parity, numeric bounds #22 onwards.

Checklist

• My code follows the contributor guidelines
• I have added tests that prove my fix/feature works
• Existing tests pass locally with my changes

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