docs: Update AGENTS.md with theme stylesheet guidelines and component…

[dkalinovInfra]

Description

Updates the UI Components section of skills/AGENTS.md:

• Adds a Theme stylesheets bullet:
  • Base theme path: _content/IgniteUI.Blazor/themes/<variant>/<theme>.css.
  • Full grids (IgbGrid, IgbTreeGrid, IgbHierarchicalGrid, IgbPivotGrid) also need _content/IgniteUI.Blazor/themes/grid/<variant>/<theme>.css.
  • The GridLite stylesheet is only for apps where IgbGridLite is the only Ignite UI component. It shouldn't be linked next to other components.
• Rewrites the "don't write names from memory" bullet so it no longer points to skills/ files that may not be installed. It names the skills, says this file is meant to ship with them (with a link to the repo), and points to the official docs if neither is available.
• Adds a bullet to handle IgbButton / IgbIconButton clicks with @onclick. There's no Click/OnClick event parameter, and ClickAsync() only triggers a click from code.

Motivation / Context

These changes come from evaluating agents that had only AGENTS.md and no skills:

• Full-grid scenarios (G1) failed 0 of 5 because the grid theme stylesheet was missing.
• When the skills weren't installed, the file referred agents to files that didn't exist.
• At least one failure came from linking the GridLite stylesheet next to other components, and at least one from using a non-existent Click parameter on IgbButton.

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

Component(s) / Area(s) Affected:

skills/AGENTS.md (agent instructions): Theming, Grids, GridLite, Button

How Has This Been Tested?

Documentation-only change. The stylesheet paths match the existing igniteui-blazor-grids and igniteui-blazor-theming skill references. The IgbButton guidance was checked against ButtonBase.cs, which has no click event parameter.

• Unit tests
• Manual testing
• Automated e2e tests

Test Configuration:

• .NET version: N/A
• Hosting model: N/A
• Browser(s): N/A
• OS: N/A

Screenshots / Recordings

N/A

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code
• This PR includes API docs for newly added methods/properties
• 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 behavioral changes and the feature specification has been updated with them
• Accessibility (ARIA, keyboard navigation, focus management) has been verified

[Copilot]

Copilot review overview

🟡 Changes recommended

The new two-stylesheet grid guidance conflicts with the preceding instruction to add only one theme stylesheet.

Review effort: Balanced
Findings: 1

Open (1)

• Clarify stylesheet count exception for full grids · New

What changed in this PR

Updates agent guidance for correct Ignite UI theming and button click handling.

Changes:

• Documents base, full-grid, and GridLite stylesheet requirements.
• Adds reliable API-reference fallbacks.
• Clarifies @onclick usage for buttons.

File	Description
skills/​AGENTS.md	Expands theming, API lookup, and click-handling guidance.

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