chore: housekeeping — linter & formatter setup

Add .prettierrc.json, .markdownlint.json, .yamllint.yaml, .gitattributes
Run CSharpier, Prettier and markdownlint across the entire codebase.
No logic changes — formatting, using order and line endings only.

.github/workflows/build.yml

@@ -11,43 +11,43 @@ name: Build
 # Dalamud SDK 15 uses on Linux).
 
 on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-  workflow_dispatch:
+    push:
+        branches: [main]
+    pull_request:
+        branches: [main]
+    workflow_dispatch:
 
 # Minimum permissions for a build-only workflow: read the repo, nothing
 # else. Closes the CodeQL "Workflow does not contain permissions" alert
 # and matches the principle-of-least-privilege the security guide
 # recommends for workflows that don't push or create releases.
 permissions:
-  contents: read
+    contents: read
 
 jobs:
-  build:
-    name: Build (Release)
-    runs-on: ubuntu-latest
-    timeout-minutes: 15
+    build:
+        name: Build (Release)
+        runs-on: ubuntu-latest
+        timeout-minutes: 15
 
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v6
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v6
 
-      - name: Setup .NET 10
-        uses: actions/setup-dotnet@v5
-        with:
-          dotnet-version: 10.0.x
+            - name: Setup .NET 10
+              uses: actions/setup-dotnet@v5
+              with:
+                  dotnet-version: 10.0.x
 
-      - name: Download Dalamud staging
-        run: |
-          hooks="$HOME/.xlcore/dalamud/Hooks/dev"
-          mkdir -p "$hooks"
-          curl -fsSL https://goatcorp.github.io/dalamud-distrib/stg/latest.zip -o dalamud.zip
-          unzip -oq dalamud.zip -d "$hooks"
+            - name: Download Dalamud staging
+              run: |
+                  hooks="$HOME/.xlcore/dalamud/Hooks/dev"
+                  mkdir -p "$hooks"
+                  curl -fsSL https://goatcorp.github.io/dalamud-distrib/stg/latest.zip -o dalamud.zip
+                  unzip -oq dalamud.zip -d "$hooks"
 
-      - name: Restore
-        run: dotnet restore HellionChat/HellionChat.csproj
+            - name: Restore
+              run: dotnet restore HellionChat/HellionChat.csproj
 
-      - name: Build (Release)
-        run: dotnet build HellionChat/HellionChat.csproj --configuration Release --no-restore
+            - name: Build (Release)
+              run: dotnet build HellionChat/HellionChat.csproj --configuration Release --no-restore