A tab is never indentation, so flow-collection content reached through a
tab below the continuation indent ('- [' / '\tfoo') is malformed even
though the tab inflates the column. A tab at or past the indent is
separation, and a tab-only blank line stays blank, so both remain valid.
Track a tab in a flow continuation's leading whitespace below the
parent + 1 indent and reject content (but not a closing bracket) reached
through it. Surpasses libyaml on Y79Y/003; whole-suite conformance
400/402, canonical events 308/308.
YAML requires multi-line flow content to be indented past the enclosing
block context (s-flow-line-prefix). libyaml does not enforce this, so
'flow: [a,' / 'b]' with 'b' in column 0, and the equivalent multi-line
flow mapping, wrongly parsed.
Track whether reaching a token crossed a line break, and in flow context
reject a token at or below the parent block indent. A closing ']' / '}'
or a leading ',' may sit at any indentation, so those are exempt (a flow
mapping's closing brace in column 0 stays valid).
Surpasses libyaml on 9C9N, VJP3/00; whole-suite conformance 394/402,
canonical events 308/308.
Per ns-plain-first a '-' starts a plain scalar in flow only when a
flow-safe character follows. A '-' before a flow indicator ('[-]',
'[-, -]') cannot start a node, but the port (like libyaml) read it as the
scalar '-'.
Reject that form in the indicator dispatch. Extract scan_to_next_token,
the comment validator, and blankLineAhead into LibYAML.Scanner.SkipToToken
to keep the fetch file within the length limit.
Surpasses libyaml on G5U8, YJV2; whole-suite conformance 390/402,
canonical events 308/308.
