refactor(rules): split angular.md into index + references

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

shared/rules/angular/references/templates-and-styling.md

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+## Templates
+
+* Keep expressions short and readable.
+* Do not execute expensive methods from templates.
+* Avoid function calls in templates when their result can be derived or cached.
+* Avoid complex conditions directly in markup.
+* Prefer derived state in TypeScript over repeated template expressions.
+* Use Angular control flow syntax such as `@if`, `@for` and `@switch` for new code.
+* Always provide stable tracking for repeated collections.
+* Avoid deeply nested template structures.
+* Split large templates into focused components when it improves maintainability.
+* Avoid unnecessary DOM elements.
+* Use semantic HTML.
+* Prefer native HTML behavior before custom implementations.
+* Keep accessibility in mind when choosing elements and interactions.
+
+## Styling
+
+* Keep styles scoped and predictable.
+* Avoid unnecessary global CSS.
+* Follow the project's styling strategy consistently.
+* Avoid excessive specificity.
+* Avoid `!important` unless there is a concrete reason.
+* Prefer reusable design tokens and shared styles over duplicated magic values.
+* Keep component styles focused on component concerns.
+* Avoid styling based on fragile DOM structure.
+* Do not mix multiple styling approaches without need.