fix: add missing lib paths to project manifests

[omerbek]

Summary

Fixes #60.

Adds the missing path = "src/lib.rs" entry to both template miden-project.toml manifests.

Why

midenc requires [lib].path in these manifests. Without it, a freshly generated project can fail immediately with unable to parse project manifest: missing field path, even though the source file exists at the conventional src/lib.rs location.

Changes

• Added [lib].path to contracts/counter-account/miden-project.toml.
• Added [lib].path to contracts/increment-note/miden-project.toml.

Testing

• git diff --check
• Parsed both edited manifests with Python tomllib and confirmed lib.path == "src/lib.rs".

I attempted to run the Miden build commands locally, but this Windows environment does not have the miden CLI on PATH. cargo miden also could not be verified because rustup failed while recovering/installing the repo's pinned nightly-2026-04-30 toolchain.