refactor: clarify hook service responsibilities and eliminate duplication

[thomhurst]

Summary

This PR improves code clarity and maintainability in the hook services by:

• Renaming services to reflect their responsibilities - Making the codebase easier to understand
• Eliminating ~170 lines of duplication - Using a generic helper method for hook delegate building

Changes

1. Renamed Hook Registrar Services

• IHookDiscoveryService → IHookRegistrar
• SourceGenHookDiscoveryService → SourceGenHookRegistrar
• ReflectionBasedHookDiscoveryService → ReflectionHookRegistrar

Why: The old name "Discovery" was ambiguous. The new name "Registrar" clearly indicates these services register hook metadata into Sources collections.

2. Renamed Hook Delegate Builder Services

• IHookCollectionService → IHookDelegateBuilder
• HookCollectionService → HookDelegateBuilder

Why: The old name "Collection" was confusing (sounded like it was finding hooks). The new name "DelegateBuilder" clearly indicates it builds executable Func<> delegates from hook metadata.

3. Code Deduplication

• Added generic BuildGlobalHooksAsync<THookMethod, TContext>() helper method
• Converted 10 nearly-identical methods (~15 lines each) into one-liners
• Result: ~170 lines of duplication reduced to ~20 lines (88% reduction)

Before:

private async Task<IReadOnlyList<Func<TestSessionContext, CancellationToken, Task>>> BuildGlobalBeforeTestSessionHooksAsync()
{
    var allHooks = new List<(int order, int registrationIndex, Func<TestSessionContext, CancellationToken, Task> hook)>(Sources.BeforeTestSessionHooks.Count);
    foreach (var hook in Sources.BeforeTestSessionHooks)
    {
        var hookFunc = await CreateTestSessionHookDelegateAsync(hook);
        allHooks.Add((hook.Order, hook.RegistrationIndex, hookFunc));
    }
    return allHooks.OrderBy(h => h.order).ThenBy(h => h.registrationIndex).Select(h => h.hook).ToList();
}
// ... 9 more nearly identical methods

After:

private Task<IReadOnlyList<Func<TestSessionContext, CancellationToken, Task>>> BuildGlobalBeforeTestSessionHooksAsync()
    => BuildGlobalHooksAsync(Sources.BeforeTestSessionHooks, CreateTestSessionHookDelegateAsync);
// ... 9 more one-liners

Impact

✅ No behavior changes - Internal refactoring only
✅ No breaking changes - All public APIs unchanged
✅ Builds successfully - Zero warnings or errors
✅ Same performance - Eager initialization preserved
✅ Better maintainability - Clear responsibilities, less duplication

Test Plan

• Builds successfully on all target frameworks
• Existing test suite passes
• No snapshot test changes required

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.