feat: add copilot instructions, workflows, and architecture docs

Co-authored-by: anakrish <35780660+anakrish@users.noreply.github.com>

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,38 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+#
+name: "Copilot Setup Steps"
+
+# Automatically run the setup steps when they are changed to allow for easy
+# validation, and allow manual testing through the repository's "Actions" tab.
+on:
+    workflow_dispatch:
+    push:
+        paths:
+            - .github/workflows/copilot-setup-steps.yml
+    pull_request:
+        paths:
+            - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+    # The job MUST be called `copilot-setup-steps` or it will not be picked up
+    # by Copilot.
+    copilot-setup-steps:
+        runs-on: ubuntu-latest
+
+        permissions:
+            contents: read
+
+        steps:
+            - name: Checkout code
+              uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+            - name: Setup Rust toolchain
+              uses: ./.github/actions/toolchains/rust
+
+            - name: Cache cargo
+              uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4 # v2.9.1
+              with:
+                  shared-key: ${{ runner.os }}-regorus
+
+            - name: Fetch dependencies
+              run: cargo fetch --locked