S2 EsLint implementation

README.md

@@ -169,6 +169,53 @@ backend on port 8080. Frontend builds and tests run independently of Maven:
 `npm run build` and `npm test`. See the frontend README for browser tests and
 production hosting requirements.
 
+## Frontend lint and formatting
+
+Run these commands from `agiledancers-fe/`:
+
+```sh
+npm run lint
+npm run lint:fix
+```
+
+`lint` checks maintained application code, inline and external Angular templates,
+unit tests, Playwright tests and JavaScript/TypeScript configuration. It uses the
+recommended JavaScript, Angular and type-aware TypeScript rules. It changes no
+files; both errors and warnings cause failure. Dependencies, generated output
+and `package-lock.json` are excluded. `lint:fix` applies ESLint's available fixes;
+review the diff and resolve any remaining findings manually. Prettier retains
+responsibility for formatting with the existing configuration.
+
+Every branch pipeline runs `npm run lint` immediately after frontend `npm ci`,
+before frontend tests/builds and container E2E. Failure prevents image publication;
+findings are in the job log and retained `ci/artifacts/verify.log`. CI only checks
+and never fixes or stages source files.
+
+Local `npm ci` automatically installs Husky at the repository root. Its commit
+hook runs **Prettier only**, through lint-staged with backup, rollback and hiding
+of unstaged changes in partially staged files enabled. It formats applicable
+staged frontend TypeScript, JavaScript, HTML, CSS and JSON files, then stages the
+formatting. Unrelated unstaged edits and files remain outside the commit. A
+formatter error or a conflict restoring unstaged edits aborts the commit and
+restores the original staged and unstaged state. Generated files are excluded;
+commits without applicable frontend changes skip these checks.
+
+The complete Prettier-plus-ESLint hook exceeds the agreed three-second budget
+when all maintained files are staged. The selected Prettier-only hook meets the
+budget for single-file, mixed and all-file commits. ESLint is therefore run
+explicitly during development and always by CI. See [S2 validation](docs/s2-validation.md)
+for the measured environment, timings and preservation checks.
+
+Hook installation is skipped when `CI` is set (including Docker builds) or
+`HUSKY=0`. Use `HUSKY=0 npm ci` to skip local installation, `HUSKY=0 git commit`
+to skip one hook execution, or `git config --local core.hooksPath /dev/null` to
+disable hooks for this clone. A subsequent normal `npm ci` enables them again.
+
+VS Code recommends the ESLint extension in both root and frontend workspaces.
+With it installed, findings appear in the editor and Problems panel; the root
+workspace selects `agiledancers-fe/` as ESLint's working directory. No automatic
+fixing or formatting on save is required. `npm run lint` uses the same rules as CI.
+
 ## Gitea CI
 
 Every branch push builds and tests both applications and their Docker images.