ci/SONARQUBE.md

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+# SonarQube static analysis
+
+Each code repo in the Runic Gateway org reports static-analysis results to the
+self-hosted **SonarQube** server for review. Analysis is **non-blocking**: it
+runs on push to `main` (i.e. *after* merge), never on pull requests, so it never
+gates a PR. It complements each repo's PR gate and release pipeline — it only
+feeds the dashboard.
+
+## Server
+
+- **URL:** `https://sonar.whitlocktech.com`
+- Each repo is a separate SonarQube project, keyed as below.
+
+## Projects
+
+| Repo | Project key | Sources analysed | Language |
+|---|---|---|---|
+| `website` | `runic-gateway-website` | `server/src`, `client/src`, `bot/src` | JS/TS |
+| `link` | `runic-gateway-link` | `sidecar/src` | Rust |
+| `Android-app` | `runic-gateway-android-app` | `app/src/main` | Kotlin |
+
+## How it's wired
+
+Each repo carries two files, identical in shape across repos:
+
+- **`sonar-project.properties`** (repo root) — declares the project key, sources,
+  tests, and exclusions. The Sonar scanner reads this.
+- **`.gitea/workflows/sonarqube.yml`** — a `SonarQube` workflow that, on push to
+  `main` (and via manual `workflow_dispatch`), checks out with full history
+  (`fetch-depth: 0`, needed for accurate blame + "new code") and runs
+  `sonarsource/sonarqube-scan-action@v4`.
+
+The scan is **source-based** — it does not build the project or run a language
+toolchain, so the workflows are lightweight (checkout + scan only). Richer
+signals (Rust Clippy, Android Lint, JaCoCo coverage) are left as documented,
+commented-out enrichment in each repo's `sonar-project.properties`; enable them
+per repo when wanted.
+
+## One-time setup per repo (Gitea UI → Repo → Settings → Actions)
+
+Both are consumed by the scan action via `env:` in the workflow:
+
+- **Secret `SONAR_TOKEN`** — a SonarQube *Analysis* token (My Account →
+  Security in SonarQube; project-scoped or global).
+- **Variable `SONAR_HOST_URL`** — the SonarQube base URL reachable from the
+  self-hosted runner. Kept as a **variable, not committed**, so the internal
+  address stays out of git.
+
+The self-hosted `ubuntu-latest` runner must be able to reach `SONAR_HOST_URL` on
+the network. Nothing waits on the SonarQube Quality Gate, so a failing gate does
+not fail the job — check the dashboard.
+
+## Adding a new repo
+
+1. Create the project in SonarQube; note its key.
+2. Add `sonar-project.properties` (copy an existing repo's, adjust key + sources).
+3. Add `.gitea/workflows/sonarqube.yml` (copy verbatim — it's language-agnostic).
+4. Set the `SONAR_TOKEN` secret and `SONAR_HOST_URL` variable in the repo's
+   Gitea Actions settings.