Add language prefixes for inline code

[ioquatix]

Summary

This adds opt-in language annotations for inline code spans through CMARK_OPT_INLINE_CODE_INFO and the CLI flag --inline-code-info.

Ruby code: ruby:`Object.new`

With the option enabled, this renders as:

<p>Ruby code: <code class="language-ruby">Object.new</code></p>

Without the option, the language prefix remains literal text:

<p>Ruby code: ruby:<code>Object.new</code></p>

Language identifiers begin with an alphanumeric character and may additionally contain _, -, +, #, and .. Examples include c++, c#, objective-c, and ruby_template.

Behavior

• A language prefix is recognized only when immediately followed by a complete inline code span.
• Ordinary punctuation after inline code remains untouched, for example Use `x`: then continue.
• Empty, quoted, invalid, and unclosed prefixes remain literal Markdown.
• CommonMark output preserves the prefix syntax and round-trips it.
• HTML output uses class="language-..."; XML output exposes the language in the info attribute.
• Smart-punctuation mode recognizes language identifiers before processing _, -, or ..

API

• Adds cmark_node_get_code_info and cmark_node_set_code_info for code blocks and inline code spans.
• Inline setters validate the language identifier and treat an empty or null value as clearing it.
• Existing cmark_node_get_fence_info and cmark_node_set_fence_info behavior remains restricted to code blocks and front matter.
• Inline language parsing remains disabled unless CMARK_OPT_INLINE_CODE_INFO is selected.

Validation

Passing:

• Inline language round-trip tests.
• Smart-punctuation inline language round-trip tests.
• Regression tests for disabled parsing and punctuation preservation.
• C API parser, accessor, setter, HTML, and CommonMark assertions.
• AddressSanitizer runs for both inline language test suites.

The complete test suite retains four failures already present on the base branch: two standalone inline-node newline assertions and the <m:abc> autolink expectation in three test variants.