Align JsonEngine method names with YamlEngine

[terrymanu]

No description provided.

[terrymanu]

Result

Review Result: Mergeable

The PR consistently renames all JsonEngine methods and updates every repository call site without changing behavior.

Evidence

• GitHub and local triple-dot scopes match: 33 files.
• No remaining references to the removed method names exist at the PR head.
• infra/util tests pass: 69 tests, 0 failures.
• No correctness blockers identified.

Coverage

Reviewed head 8544858cbab2efe8adec088a2999d94712b9ea16 against base ead5993a981309a124f067eb6d89c077c69e7b59.

Reviewed all 33 changed files across the JSON API rename cluster, including production callers, unit tests, E2E tests, and integration parser code. Completed root-cause, blast-radius/contracts, tests/runtime, and convergence reviews.

This is a code-scope result only; CI was not reviewed.