feat(combo): add disableClear input to IgxCombo and IgxSimpleCombo

[Copilot]

The clear button on igx-combo and igx-simple-combo was always rendered with no opt-out, causing UX issues for required fields and focus-trap problems in dialogs (button remains focusable even when hidden via CSS).

Changes

• IgxComboBaseDirective (combo.common.ts) — adds disableClear: boolean input (default false), inherited by both combo variants
• combo.component.html / simple-combo.component.html — gates clear button rendering on !disableClear
• Tests — 3 specs each for IgxComboComponent and IgxSimpleComboComponent covering default value, hidden state, and visible state
• README / CHANGELOG — updated accordingly

Usage

<!-- Clear button is fully removed from the DOM when disableClear is true -->
<igx-combo [disableClear]="true" [data]="items" valueKey="id" displayKey="name"></igx-combo>
<igx-simple-combo [disableClear]="true" [data]="items" valueKey="id" displayKey="name"></igx-simple-combo>

Original prompt

---

This section details on the original issue you should resolve

<issue_title>SimpleCombo: add possibility to hide clear button</issue_title>
<issue_description>## Is your feature request related to a problem? Please describe.
The clear button is always visible. For specific uses cases I wish I could hide it, for example if the field is required and it doesn't make sense to clear the input.

Describe the solution you'd like

Please add a possiblity to hide the clear button.

Describe alternatives you've considered

I tried hiding it via css, but because it is still focusable (tabindex=0) there are problems when using it inside a dialog with focus trap.</issue_description>

<agent_instructions>The IgcComboComponents implements disableClear input, which should also be applied to the IgxCombos. </agent_instructions>

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

• Fixes SimpleCombo: add possibility to hide clear button #16705

---

💬 Send tasks to Copilot coding agent from Slack and Teams to turn conversations into code. Copilot posts an update in your thread when it's finished.