Mark namespace classes as final with private constructors

[Copilot]

Several implementation classes serving as static method containers were missing proper namespace class protections.

Changes

Modified 7 classes to prevent instantiation and inheritance:

• TypeClasses - Main API entry point
• ConstructorLookup - Witness rule discovery
• OverlappingInstances - Instance overlap resolution
• Unification - Type unification and substitution
• WitnessInstantiation - Plan compilation and interpretation
• WitnessResolution - Resolution logic
• WitnessSummoning - High-level summoning orchestration

Each class now declared final with a private empty constructor, matching the existing pattern in Maps, Functions, and Lists utility classes.

public final class Unification {
  private Unification() {}
  
  public static Maybe<Map<ParsedType.Var, ParsedType>> unify(ParsedType t1, ParsedType t2) {
    // ...
  }
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https src/main/java/com/garciat/typeclasses/impl/WitnessResolution.java src/main/java/com/garciat/typeclasses/impl/WitnessRule.java src/main/java/com/garciat/typeclasses/impl/WitnessSummoning.java (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Namespace classes: make them final and private constructor</issue_title>
<issue_description>There are several implementation classes that only serve as namespaces for static methods. They should be marked final and have private and empty constructors.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Namespace classes: make them final and private constructor #12

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.04%. Comparing base (a20633c) to head (e099896).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #13      +/-   ##
============================================
+ Coverage     67.26%   68.04%   +0.77%     
  Complexity      234      234              
============================================
  Files            49       49              
  Lines           611      604       -7     
  Branches         46       46              
============================================
  Hits            411      411              
+ Misses          177      170       -7     
  Partials         23       23              

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