refactor(ide): model source token resolution

[hongjr03]

Summary

• Introduce a source token resolution result that separates resolved selections from blocked source-domain claims.
• Preserve preprocessor-owned unavailable and ambiguous states without routing them through normal syntax tokens.
• Update hover, navigation, highlights, and references to consume resolved source-token selections through the shared API.

Validation

• cargo check -p ide
• cargo test -p ide
• cargo clippy -p ide --all-targets -- -D warnings
• git diff --check

[github-actions]

Docs preview: https://vide.pascal-lab.net/preview/pr-241/