Implement delimiter-aware N-quoted strings

[delaneyj]

Upstream: starfederation/ron#33
Related escape update: #1

Problem

The universal escape rules currently described in #1 include rejecting raw double quotes in every string form. The upstream reference has identified that as a flaw: it defeats N-quote framing and makes embedded JSON unnecessarily noisy.

Intended RON:

data ['{"coordinates":[12.5,-42.25],"type":"Point"}']

Not:

data ['{\"coordinates\":[12.5,-42.25],\"type\":\"Point\"}']

Required behavior

When implementing #1 against the corrected upstream corpus:

• Keep JSON escape decoding in every string form.
• Keep \\, control-character escapes, Unicode handling, and raw C0 rejection.
• Permit raw double quotes inside apostrophe-delimited strings.
• Permit quote runs shorter than the active N-quote delimiter.
• Keep \" as accepted input.
• Do not unconditionally escape double quotes before selecting the rendering delimiter.

Acceptance

• The raw embedded-JSON example parses and round-trips.
• JSON-to-RON renders that value without \".
• Repeated-double-quote framing accepts internal shorter quote runs.
• The implementation passes the corrected upstream conformance corpus.