refactor(docs-infra): migrate @angular/docs from dev-infra into adev directory (#57132)

To increase the ease of development we are moving @angular/docs into the adev directory within this repo. While
we are doing this to improve our development experience in the short term, efforts are also in place
to maintain a division between this @angular/docs (shared) code and adev itself, so that it can be extracted
back out in the future when components is ready to leverage it as well.

PR Close #57132

adev/shared-docs/components/search-dialog/search-dialog.component.scss

@@ -0,0 +1,147 @@
+dialog {
+  background-color: transparent;
+  border: none;
+  padding-block-end: 3rem;
+
+  &::backdrop {
+    backdrop-filter: blur(5px);
+  }
+}
+
+.docs-search-container {
+  width: 750px;
+  max-width: 90vw;
+  background-color: var(--page-background);
+  border: 1px solid var(--senary-contrast);
+  border-radius: 0.25rem;
+  box-sizing: border-box;
+
+  .docs-search-input {
+    border-radius: 0.25rem 0.25rem 0 0;
+    border: none;
+    border-block-end: 1px solid var(--senary-contrast);
+    height: 2.6875rem; // 43px;
+    padding-inline-start: 1rem;
+    position: relative;
+
+    &::after {
+      content: 'Esc';
+      position: absolute;
+      right: 1rem;
+      color: var(--gray-400);
+      font-size: 0.875rem;
+    }
+  }
+
+  ul {
+    max-height: 50vh;
+    overflow-y: auto;
+    list-style-type: none;
+    padding-inline: 0;
+    padding-block-start: 1rem;
+    margin: 0;
+    border-block-end: 1px solid var(--senary-contrast);
+
+    li {
+      border-inline-start: 2px solid var(--senary-contrast);
+      margin-inline-start: 1rem;
+      padding-inline-end: 1rem;
+      padding-block: 0.25rem;
+
+      a {
+        color: var(--secondary-contrast);
+        display: flex;
+        justify-content: space-between;
+        gap: 0.5rem;
+
+        .docs-search-result-icon {
+          i {
+            display: flex;
+            align-items: center;
+            font-size: 1.2rem;
+          }
+        }
+      }
+
+      &.active {
+        background-color: var(--septenary-contrast); // stylelint-disable-line
+      }
+
+      &:hover,
+      &.active {
+        background-color: var(--octonary-contrast); // stylelint-disable-line
+        border-inline-start: 2px solid var(--primary-contrast);
+        a {
+          span:not(.docs-result-page-title),
+          .docs-search-results__type {
+            color: var(--primary-contrast);
+            i {
+              color: var(--primary-contrast);
+            }
+          }
+        }
+      }
+    }
+
+    .docs-search-result-icon,
+    .docs-search-results__type,
+    .docs-result-page-title {
+      color: var(--quaternary-contrast);
+      display: inline-block;
+      font-size: 0.875rem;
+      transition: color 0.3s ease;
+      padding: 0.75rem;
+      padding-inline-end: 0;
+    }
+
+    .docs-search-results__lvl2 {
+      display: inline-block;
+      margin-inline-start: 2rem;
+      padding-block-start: 0;
+    }
+
+    .docs-search-results__lvl3 {
+      margin-inline-start: 2rem;
+      padding-block-start: 0;
+    }
+  }
+
+  .docs-result-page-title {
+    font-size: 0.875rem;
+    font-weight: 400;
+  }
+}
+
+.docs-search-results__start-typing,
+.docs-search-results__no-results {
+  padding: 0.75rem;
+  color: var(--gray-400);
+}
+
+.docs-result-icon-and-type {
+  display: flex;
+
+  .docs-search-results__type {
+    padding-inline-start: 0;
+  }
+}
+
+.docs-algolia {
+  display: flex;
+  align-items: center;
+  justify-content: end;
+  color: var(--gray-400);
+  padding: 1rem;
+  font-size: 0.75rem;
+  font-weight: 500;
+  gap: 0.25rem;
+  background-color: var(--page-background);
+  border-radius: 0 0 0.25rem 0.25rem;
+
+  docs-algolia-icon {
+    display: inline-flex;
+    margin-block-start: 0.12rem;
+    margin-inline-start: 0.15rem;
+    width: 4rem;
+  }
+}