feat(toolchain): adopt Biome, oxlint, attw; keep eslint-config-next + knip

.editorconfig

@@ -0,0 +1,15 @@
+# EditorConfig (https://editorconfig.org) - matches the Biome formatter settings
+# so editors agree before Biome ever runs.
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.md]
+# Markdown hard line breaks are two trailing spaces; do not strip them.
+trim_trailing_whitespace = false

.github/workflows/ci.yml

@@ -29,7 +29,10 @@ jobs:
       - name: Install dependencies
         run: bun install --frozen-lockfile
 
-      - name: Run ESLint
+      - name: Check formatting (Biome)
+        run: bun run format
+
+      - name: Run linters (oxlint + ESLint)
         run: bun run lint
 
       - name: Run TypeScript type check
@@ -48,6 +51,12 @@ jobs:
           USER_EMAIL: user@libredb.org
           USER_PASSWORD: test-user
 
+      - name: Build library package (tsup)
+        run: bun run build:lib
+
+      - name: Check package types resolution (attw)
+        run: bun run attw
+
   test:
     name: Unit & Integration Tests
     runs-on: ubuntu-latest

.gitignore

@@ -111,3 +111,7 @@ data/
 
 docs/superpowers/
 
+# attw packaging scratch (type-resolution check)
+.attw/
+*.tgz
+

.oxlintrc.json

@@ -0,0 +1,42 @@
+{
+  "$schema": "https://raw.githubusercontent.com/oxc-project/oxc/main/npm/oxlint/configuration_schema.json",
+  "plugins": ["typescript", "oxc", "react", "react-hooks", "jsx-a11y", "nextjs", "import"],
+  "categories": {
+    "correctness": "error",
+    "suspicious": "error",
+    "perf": "warn",
+    "pedantic": "off",
+    "style": "off"
+  },
+  "rules": {
+    "react/react-in-jsx-scope": "off",
+    "react/no-unstable-nested-components": "off",
+    "import/no-unassigned-import": "off",
+    "import/no-named-as-default": "off",
+    "react-hooks/exhaustive-deps": "off",
+    "no-unused-vars": "off",
+    "no-underscore-dangle": "off",
+    "no-shadow": "off",
+    "no-control-regex": "off",
+    "jsx-a11y/no-static-element-interactions": "warn",
+    "jsx-a11y/click-events-have-key-events": "warn",
+    "jsx-a11y/label-has-associated-control": "warn",
+    "jsx-a11y/prefer-tag-over-role": "warn",
+    "jsx-a11y/no-autofocus": "warn",
+    "jsx-a11y/control-has-associated-label": "warn",
+    "jsx-a11y/no-noninteractive-element-interactions": "warn",
+    "jsx-a11y/anchor-has-content": "warn"
+  },
+  "overrides": [
+    {
+      "files": ["tests/**", "**/*.test.ts", "**/*.test.tsx"],
+      "rules": {
+        "typescript/no-extraneous-class": "off",
+        "no-useless-constructor": "off",
+        "no-new": "off",
+        "no-constant-binary-expression": "off"
+      }
+    }
+  ],
+  "ignorePatterns": ["dist/**", ".next/**", "out/**", "build/**", "coverage/**", "node_modules/**", "next-env.d.ts"]
+}

CLAUDE.md

@@ -24,14 +24,19 @@ Web-based SQL IDE for cloud-native teams: PostgreSQL, MySQL, SQLite, Oracle, SQL
 bun install              # deps (Bun preferred)
 bun dev                  # dev server (Turbopack)
 bun run build            # production build
-bun run lint             # ESLint 9
+bun run format           # Biome formatter check (format:fix to write); CSS/JSON excluded
+bun run lint             # oxlint (fast, syntactic) then ESLint 9 (eslint-config-next + narrow type-aware layer)
+bun run lint:oxc         # oxlint only
 bun run typecheck        # TypeScript strict
 bun run test             # all layers: unit + api + integration + hooks + components
 bun run test:e2e         # Playwright (requires build)
 bun run test:coverage    # coverage report
 bun run build:lib        # tsup → @libredb/studio package dist (see rule below)
+bun run attw             # validate published type-resolution against the packed tarball (needs build:lib first)
 ```
 
+> **Toolchain rationale (Biome formatter, oxlint, type-aware ESLint layer, attw) lives in [`docs/TOOLCHAIN.md`](docs/TOOLCHAIN.md).** Biome is formatter-only (lineWidth 120); oxlint is the fast syntactic layer in front of ESLint; `eslint-config-next` still owns React/Next/hooks; a narrow `typescript-eslint` type-aware layer guards `src/app/api` + `src/lib/db` against floating promises; attw uses `--profile node16` (the package targets Node >=24 + modern bundlers, so node10 is ignored).
+
 > **`build:lib` after platform-facing changes:** after changing any component used by platform (workspace, providers, …), run `build:lib` — `bun run build` (Next.js) does NOT update the package dist.
 
 > **Tests — always `bun run test`, never bare `bun test`.** Component tests need isolated execution groups (`tests/run-components.sh`) to avoid `mock.module()` cross-contamination.
@@ -40,7 +45,7 @@ bun run build:lib        # tsup → @libredb/studio package dist (see rule below
 
 ## Pre-Commit Verification (MANDATORY)
 
-After every code change, run all four locally before claiming done — they match CI (`ci.yml`, `docker-build-push.yml`): `bun run lint` · `bun run typecheck` · `bun run test` · `bun run build`. A local pass on all four guarantees CI passes; do not skip any.
+After every code change, run all five locally before claiming done — they match CI (`ci.yml`, `docker-build-push.yml`): `bun run format` · `bun run lint` · `bun run typecheck` · `bun run test` · `bun run build`. A local pass guarantees CI passes; do not skip any. (`bun run lint` runs oxlint then ESLint; the CI `lint-and-build` job additionally runs `build:lib` + `attw`.)
 
 ## Architecture
 

biome.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.5.1/schema.json",
+  "vcs": { "enabled": true, "clientKind": "git", "useIgnoreFile": true },
+  "files": {
+    "includes": ["src/**", "tests/**", "e2e/**", "scripts/**", "*.ts", "*.mts", "*.mjs"]
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineWidth": 120
+  },
+  "javascript": {
+    "formatter": {
+      "quoteStyle": "double",
+      "semicolons": "always"
+    }
+  },
+  "css": { "formatter": { "enabled": false } },
+  "json": { "formatter": { "enabled": false } },
+  "linter": { "enabled": false },
+  "assist": { "enabled": false }
+}