refactor(json-document): unify replace validation

[developer-1px]

Summary

• consolidate root-object, same-array, independent, and overlapping replace schema validation behind one final-target planner
• remove the duplicate schema-side array and object replace executors and dead helpers, reducing production source by 610 LOC
• preserve existing public failure ordering and fallback behavior while allowing later ancestor or descendant replacements to repair intermediate invalid values
• harden schema introspection against inherited properties and custom standalone record-key checks

Verification

• 538 tests passed, 4 skipped
• typecheck, build, package smoke, layer check, standard conformance, and docs evaluation passed
• differential checks: 48,400 independent batches and 19,872 dash/catchall batches with zero contract differences
• adapter readiness passed: Editable p95 4.016ms / 14ms, Canvas single p95 0.328ms / 4ms, Canvas batch p95 5.107ms / 8ms
• one noisy core wide-root sample measured 20.99ms / 20ms; 61-run interleaved comparison measured branch CPU p50 12.78ms versus main 15.36ms, indicating no refactor regression

Contract

• no public API surface changes
• legacy diagnostic ordering remains behind explicit compatibility fallbacks
• overlapping replace batches validate effective final targets after one atomic apply