Improve InputNumber test coverage and add missing scenarios

[VigneshwaranGovindharajan]

Description

This PR significantly enhances the test coverage of the Blazor InputNumber component by adding 69 new test cases, increasing the total test count from 5 to 74 with 100% pass rate.

Original Test Count: 5 tests
New Tests Added: 69 test cases
Final Test Count: 74 tests (100% pass rate)

Test Categories Added:

Validation & Error Handling (12 tests)

• DisplayAttribute name usage in validation messages
• Field name fallback when DisplayName is missing
• Custom parsing error messages
• Validation message updates on parsing errors
• Unsupported numeric types (Guid) throwing during rendering

Type Support & Parsing (25 tests)

• Integer types: int, long, short (min/max boundary values)
• Floating-point types: float, double, decimal (including large values)
• Nullable variants: float?, double?, decimal?, int?, long?
• Invariant culture parsing regardless of current culture
• Null value formatting

Input Validation (15 tests)

• Whitespace handling (rejects, accepts leading/trailing)
• Scientific notation rejection
• Hex notation rejection
• Currency symbol rejection
• Double negative rejection
• Multiple decimal points rejection
• Empty string for non-nullable types
• Plus sign acceptance

Binding & Events (8 tests)

• ValueChanged callback behavior on valid/invalid input
• EditContext field change notifications
• Sequential value changes firing multiple callbacks
• Invalid input preserving previous valid value
• Multiple sequential edits

Attributes & Rendering (12 tests)

• ID attribute (generated and explicit override)
• Name attribute generation
• Value attribute reflecting current value
• Type attribute (default "number", user override to "range")
• Step attribute (default "any", custom override)
• Min/Max attributes for range control
• Custom attributes (data-testid, autocomplete, placeholder, class)
• AdditionalAttributes preservation in render tree

Format/Parse Round-Trips (4 tests)

• Format-Parse-Format consistency
• Parse-Format-Parse consistency
• Decimal round-trip with various values (0, 1, -1, 99.99, MaxValue/2)

CSS Class Behavior (2 tests)

• CSS classes added for validation state
• Valid class applied on valid input

Key Improvements:

• All tests pass (74/74)
• No breaking changes
• No public API changes
• Follows existing test patterns
• Uses proper xUnit assertions
• Covers both EditContext-integrated and standalone scenarios

Test Results:

Impact:

• Eliminates previous coverage gaps for InputNumber component
• Strengthens regression protection for numeric input behavior
• Validates all numeric types and their edge cases
• Ensures proper validation, binding, and rendering behavior
• Covers both positive and negative scenarios (invalid inputs)

PR Checklist

• Small and focused — Only test improvements for InputNumber
• Tests added — 69 new test cases added
• Code style matches — Follows existing patterns
• Local build passes
• Local tests pass (74/74)
• No breaking changes
• Issue linked (if applicable) — Not applicable
• Public API updates — Not applicable
• XML documentation — Not applicable

[dotnet-policy-service]

Thanks for your PR, @VigneshwaranGovindharajan. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.