Routes the value and stream APIs through the ported scanner+parser (the
event API already was), so PureYAML now parses entirely on the libyaml
port. Adds the features needed to match and exceed the previous engine:
JSON UTF-16 surrogate-pair \u escapes, bare documents after an explicit
`...`, reserved-directive handling that still requires a following `---`,
and a 64-level nesting bound enforced on the event stream so deeply nested
input fails with nestingTooDeep instead of overflowing a recursive
consumer. Parser errors are translated to the diagnostic-aware ParseError,
recovering precise codes where identifiable and a readable malformed
fallback otherwise; error-reporting fixtures are rebased onto the port.
Canonical event conformance: 268 -> 271 of 308 (7Z25, HWV9, QT73).
393 tests pass.
Compose an empty scalar wherever a node is grammatically required but the next token is a structural indicator or line/stream end, mirroring libyaml's process_empty_scalar: after a tag or anchor property with no node, as an absent mapping value (block and flow), as an absent mapping key (both the plain ': v' form and the explicit '?' form), in flow empty key/value forms ({ : }, { , : v }), and for an indented block node following properties. Also fixes a pre-existing block-sequence bug that nested a sibling '-' as a child when only properties remained on the entry line.
Empty scalars resolve through the existing resolver against the empty string, so !!str yields the empty string, bare empty or !!null yields null, and an empty key yields the empty string.
Flips 20 official YAML test suite cases to passing (270/402). CT4Q no longer false-rejects but still value-mismatches on flow plain-scalar folding (a separate gap), so it is reclassified in the manifest rather than removed. Updates the gap manifest, fixtures, counts, and roadmap.
