Ignore wikilink markers inside inline code

[cobymyers]

Fixes #269

/claim #269

Summary

• filter parsed references that overlap inline/fenced code spans when references_in_codeblocks is disabled
• prevents literal inline-code markers like `[[` and `]]` from becoming a fake unresolved wikilink
• adds regression coverage plus a control case for a real wikilink next to inline code

Verification

• cargo fmt --check
• cargo test wiki_link -- --nocapture
• cargo test
• git diff --check

Payout note: this is for the $5 Algora bounty. GitHub Sponsors is also available at https://github.com/sponsors/cobymyers if the maintainer prefers a direct one-time sponsor route.