feat: release 15.0.0

[johnhwhite]

AB#3643175

This release updates the repository to SKY UX 15.0.0. It updates Angular peer dependency minimums to 22.2.0, aligns Sky UX package ranges with stable 15.0.0, and updates the root dependencies and supported Node.js and npm versions.

The playground and library test configurations remove the custom polyfills configuration. The playground polyfills file is deleted. The stache package updates its ngAdd install range and moves several test imports to @skyux/core/testing. The stache JSON data service now explicitly returns undefined when a requested property or nested key is missing.

The .coderabbit.yaml file from the coderabbit repository in ADO is being used: https://dev.azure.com/blackbaud/Products/_git/coderabbit

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⚙️ Run configuration

Configuration used: Repository: blackbaud/coderabbit/.coderabbit.yaml

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Plan: Enterprise

Run ID: 923993bb-fa1d-4c8e-8c4f-a58cb1af758f

📥 Commits

Reviewing files that changed from the base of the PR and between 479dc9b and b8a2808.

⛔ Files ignored due to path filters (1)

• package-lock.json is excluded by !**/package-lock.json

📒 Files selected for processing (23)

• .versionrc
• apps/playground/project.json
• apps/playground/src/polyfills.ts
• apps/playground/tsconfig.app.json
• libs/clipboard/package.json
• libs/clipboard/project.json
• libs/code-block/package.json
• libs/code-block/project.json
• libs/media/package.json
• libs/media/project.json
• libs/stache/package.json
• libs/stache/project.json
• libs/stache/schematics/ng-add/ng-add.schematic.ts
• libs/stache/src/lib/modules/action-buttons/action-buttons.component.spec.ts
• libs/stache/src/lib/modules/affix/affix-top.directive.spec.ts
• libs/stache/src/lib/modules/affix/affix.component.spec.ts
• libs/stache/src/lib/modules/back-to-top/back-to-top.component.spec.ts
• libs/stache/src/lib/modules/json-data/json-data.service.ts
• libs/stache/src/lib/modules/nav/link.directive.spec.ts
• libs/stache/src/lib/modules/shared/window-ref.spec.ts
• libs/stache/src/lib/modules/table-of-contents/table-of-contents.component.spec.ts
• libs/stache/src/lib/modules/wrapper/wrapper.component.ts
• package.json

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