Define data comparison contract v0

[MatthiasLew]

What changed

• adds an experimental closed comparison-bundle JSON Schema
• composes pinned wellmanifest/dsl query, observation and result profiles
• defines canonical scalar/set values, evidence, outcomes and typed deltas
• adds deterministic conformance checks and golden MATCH/CONFLICT fixtures
• records the bounded ticket-004 evidence

Why

ADR-001 selected EXTEND: Twin supplies useful lineage but not the complete
neutral comparison semantics. This local contract adds only the missing
data2dsl-owned semantics while reusing Wellmanifest profiles by immutable
reference and leaving neighboring repositories unchanged.

Impact

Adds an experimental, descriptive contract and validation tooling. It does not
add acquisition, network access, reasoning, effects or a stable public API.

Checks

• project\\governance-check.bat --actor agent: GOV-PASS, 0 errors, 0 warnings
• contract self-test: 5 positive outcomes, 5 negative invariants
• pinned dsl_check.py validate: DSL-PASS
• pinned dsl_check.py standards: DSL-PASS
• git diff --check