Resolve dot-relative Markdown links from source files

[Entr0zy]

Summary

/claim #274

This updates Markdown link resolution so dot-relative paths are resolved from the Markdown file containing the reference instead of being treated as workspace-root-relative. That allows nested files to resolve links such as ./target and ../target against nearby notes while preserving existing root-relative behavior for paths like folder/file.

Changes

• Pass the reference source path into the path-matching helper.
• Resolve ./ and ../ link targets relative to the source file parent before comparing them with indexed vault paths.
• Add regression coverage for same-directory and parent-directory relative links from nested files.

Verification

• git diff --check passed.
• Added targeted Rust tests for the new path matching behavior.
• Could not run cargo test in this local environment because Cargo is not installed here (spawnSync cargo ENOENT).