Fix false wikilinks from inline code markers

[jeffreybarts-max]

Fixes #269

Summary

• Ignore references whose opening or closing boundary is inside an inline/fenced code span when references_in_codeblocks is disabled.
• Add a regression test for literal `[[` and `]]` markers being reported as an unresolved wikilink.
• Add a guard test so Markdown links with inline code in their display text still parse normally.

/claim #269

Tests

• cargo fmt --check
• docker run --rm -v "${PWD}:/work" -w /work rust:1.91-bookworm cargo test

[jeffreybarts-max]

/claim #269