* docs(style): require intra-doc links for identifier mentions
Add a CODE_STYLE_GUIDE.md section telling contributors (and AI agents)
to turn identifier mentions inside `///` and `//!` doc comments into
rustdoc intra-doc links when the identifier is reachable from scope.
Intra-links give readers one-click navigation and let rustdoc surface
broken-link warnings when items are renamed or removed.
* docs(style): tighten intra-doc link guidance
Drop the redundant `//!` callout — saying "doc comment (`///` or `//!`)"
once at the top is enough; the second example only restated the rule.
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Co-authored-by: Claude <noreply@anthropic.com>