[cleanup] Phase 2a: Exclude future-use crates from workspace builds

[AlexMikhalev]

Summary

Move terraphim_build_args and terraphim-markdown-parser to workspace exclude list.

Actions

• Add terraphim_build_args to Cargo.toml exclude list
• Add terraphim-markdown-parser to Cargo.toml exclude list
• Update .release-plz.toml if needed

Verification

• cargo check --workspace passes
• cargo test --workspace passes

[AlexMikhalev]

PR #631 addresses this. Moved terraphim_build_args and terraphim-markdown-parser to workspace exclude list.