Copilot instructions and build/test skills (#2444)

* Add copilot instructions and skills for build and tests.

* Add dev-server skill.

* Auth Util changes to fix Entra login while running from copilot.

* Fix lint issue.

.github/skills/build/SKILL.md

@@ -0,0 +1,95 @@
+---
+name: build
+description: Build the Cosmos Explorer project. Use this skill when asked to build, compile, or check the build status of the project.
+allowed-tools: shell
+---
+
+# Build Skill
+
+Use the following commands to build the Cosmos Explorer project. Choose the appropriate command based on the task.
+
+## Full Production Build
+
+Run a complete production build (format check → lint → compile → strict compile → webpack prod → copy):
+
+```bash
+npm run build
+```
+
+## CI Build (Faster)
+
+Run a CI build that uses webpack dev mode for faster bundling:
+
+```bash
+npm run build:ci
+```
+
+## TypeScript Compile Only
+
+Run a TypeScript type-check without emitting output:
+
+```bash
+npm run compile
+```
+
+## Strict TypeScript Compile
+
+Run a strict null-checks compile on the subset of files in `tsconfig.strict.json`:
+
+```bash
+npm run compile:strict
+```
+
+## Lint Only
+
+Run ESLint across all `.ts` and `.tsx` files:
+
+```bash
+npm run lint
+```
+
+## Format Check
+
+Run Prettier to verify formatting without modifying files:
+
+```bash
+npm run format:check
+```
+
+## Pre-Build: Check Dependencies
+
+Before running any build command, check whether `npm install` needs to be run. Do this by comparing `package.json` and `package-lock.json` against the installed `node_modules`:
+
+1. Check if the `node_modules` directory exists. If it does not, run `npm install`.
+2. If `node_modules` exists, check whether `package.json` or `package-lock.json` have been modified more recently than `node_modules`. If so, run `npm install`.
+
+```bash
+# Check if node_modules is missing or outdated
+if [ ! -d node_modules ] || [ package.json -nt node_modules ] || [ package-lock.json -nt node_modules ]; then
+  npm install
+fi
+```
+
+On Windows PowerShell:
+
+```powershell
+if (-not (Test-Path node_modules) -or
+    (Get-Item package.json).LastWriteTime -gt (Get-Item node_modules).LastWriteTime -or
+    (Get-Item package-lock.json).LastWriteTime -gt (Get-Item node_modules).LastWriteTime) {
+    npm install
+}
+```
+
+Always run this check before proceeding with any build command.
+
+## Guidelines
+
+- When asked to simply "build", run `npm run build` for a full production build.
+- When asked for a quick or fast build, use `npm run build:ci`.
+- When asked to just check types, use `npm run compile`.
+- If the build fails, read the error output carefully. Common issues include:
+  - **TypeScript errors**: Fix type errors shown in the `npm run compile` output.
+  - **Strict null-check errors**: Fix strict errors shown in `npm run compile:strict` output.
+  - **Lint errors**: Fix lint issues shown in `npm run lint` output.
+  - **Format errors**: Run `npm run format` to auto-fix formatting, then retry the build.
+- New files must be added to `tsconfig.strict.json` so they compile under strict mode.