Add S4 CuddManager constructor and C++ wrapper with finalizer

[MEO265]

Motivation

• Provide a safe R-side S4 wrapper for the CUDD Cudd manager so R code can construct and manage a manager instance without leaking C++ memory.
• Expose a simple, idiomatic R constructor and avoid the previously exported helper name new_cudd_manager.
• Ensure proper lifetime management by creating the manager in C++ and registering an R finalizer that deletes the Cudd instance.
• Address inline review comments to avoid importing the entire methods namespace and to follow R naming conventions for constructors.

Description

• Added src/cudd_manager.cpp which implements c_cudd_new() that allocates a Cudd object, returns an external pointer, and registers a finalizer that deletes the Cudd instance.
• Declared c_cudd_new() in src/rcudd.h and registered it in src/register.cpp (added the c_cudd_new entry to R_registerRoutines).
• Added R/cudd_manager.R that defines the S4 class CuddManager, the constructor CuddManager() which calls .Call("c_cudd_new"), and a show method, and qualified S4 operations with methods:: instead of importing the namespace.
• Updated package metadata and exports by adding Imports: methods to DESCRIPTION, exporting CuddManager in NAMESPACE, and refreshing generated man files (man/CuddManager-class.Rd and man/CuddManager.Rd).

Testing

• Ran roxygen2::roxygenise() to refresh documentation after the API/name changes, which was executed after installing roxygen2.
• Built the package with R CMD build . which produced Rcudd_0.0.0.9999.tar.gz.
• Executed R CMD check --no-manual Rcudd_0.0.0.9999.tar.gz and the check completed successfully with Status: OK.

---

Codex Task

[codecov]

Codecov Report

❌ Patch coverage is 87.78409% with 129 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.24%. Comparing base (5ee1eee) to head (0c44e54).

Files with missing lines	Patch %	Lines
src/cudd_manager.cpp	86.86%	109 Missing ⚠️
R/cudd_manager.R	91.38%	10 Missing ⚠️
R/cudd_bdd.R	90.00%	4 Missing ⚠️
R/cudd_add.R	89.66%	3 Missing ⚠️
R/cudd_zdd.R	88.89%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #3      +/-   ##
==========================================
- Coverage   93.06%   89.24%   -3.82%     
==========================================
  Files           8       15       +7     
  Lines         403     1458    +1055     
==========================================
+ Hits          375     1301     +926     
- Misses         28      157     +129     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.