Fix wikilink markers inside inline code

[nexiumbiz-debug]

/claim #269

Summary

• Filter parsed references whose start or end position lands inside an inline/fenced code span when references_in_codeblocks is disabled.
• Prevent separate inline-code markers like `[[` and `]]` from being combined into one unresolved wiki reference.
• Add regression coverage for the reported case plus a control case where a real wikilink outside inline code still parses.

Verification

• cargo fmt --check
• git diff --check

Not run

• cargo test wiki_link -- --nocapture could not complete in this Windows environment because the local Rust toolchain lacked working native linker support (link.exe for MSVC; GNU fallback also lacked required MinGW GCC libraries). The attempted temporary toolchain installs were cleaned up after verification.