refactor(input-group): add styling support for more input types

[simeonoff]

Closes #17156

Description

This PR adds minimal styling support for input types date, time, datetime-local, month, and week in the context of the igx-input-group component.

Type of Change (check all that apply):

• Bug fix
• New functionality
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes)
• Documentation
• Demos
• CI/CD
• Tests
• Changelog
• Skills/Agents

Component(s) / Area(s) Affected:

The only affected component is the Input Group.

How Has This Been Tested?

• Unit tests
• Manual testing
• Automated e2e tests

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them
• Accessibility (ARIA, keyboard navigation, focus management) has been verified

[Copilot]

Pull request overview

Adds styling support in igx-input-group for native date/time-like input types to prevent label/placeholder overlap (Issue #17156), and updates the showcase to demonstrate the newly supported types.

Changes:

• Updated the Input Group showcase sample to include date, time, datetime-local, month, and week native input types (and adjusted defaults).
• Extended Material/Bootstrap input-group styling selectors to account for date/time-like inputs (label/notch behavior, disabled text coloring).
• Introduced color-scheme propagation based on theme variant to better align native control rendering with theme mode.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/app/input-group-showcase/input-group-showcase.sample.ts	Expands the demo’s selectable native input types and adjusts default selections.
projects/igniteui-angular/core/src/core/styles/components/input/_input-group-theme.scss	Adds styling rules for date/time-like native inputs to avoid label overlap and improve visual consistency.

[adrianptrv]

There is a difference in the text colors for the idle state across the input types
In Angular, the text uses --filled-text-color for both the idle and filled states, while in WC it uses --idle-text-color for the idle state and --filled-text-color for the filled state.

[adrianptrv]

The previous issues are fixed.

The only remaining thing I see is that when the input fields are empty and hovered, the text color becomes darker. I noticed that it uses the --filled-text-hover-color variable.
I don’t think the empty text color should change on hover, at least based on how the other input field texts behave.

IgniteuiDevDemos.9.mp4

When the input is filled and hovered, it works correctly:

idle => --filled-text-color
hover => --filled-text-hover-color

---

Also, when the input is empty and focused, Angular makes the entire text darker, while in Web Components only the focused part of the text becomes darker and the rest remains with the idle color. I’m not sure which behavior is the correct one.

IgniteuiDevDemos.10.mp4