[QOTD-2] Add CLAUDE.md for docs repository

Documents the architecture, stack decisions, component layout, and code
style guidelines for the Quote of the Day API implementation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md — Quote of the Day API Docs
+
+This repository contains the **specifications and architecture documents** for the Quote of the Day REST API. It is a documentation-only repo; the actual implementation lives elsewhere.
+
+---
+
+## Build Commands
+
+There is no source code in this repository — no build, install, or compilation steps apply.
+
+---
+
+## Test Commands
+
+No test suite exists in this documentation repository. Tests for the API implementation should be run via:
+
+```bash
+npm test          # run full test suite (Jest + ts-jest, or Vitest)
+npm run lint      # ESLint with TypeScript-aware ruleset; must exit cleanly
+```
+
+These commands apply to the **implementation repo**, not this one.
+
+---
+
+## Development Commands
+
+No dev server is applicable here. For the API implementation:
+
+```bash
+PORT=3000 npm start    # start Express server (defaults to port 3000)
+```
+
+---
+
+## Project Structure
+
+```
+quote-of-the-day-api-docs/
+├── README.md                  # Minimal project title placeholder
+└── architecture/
+    ├── tad.md                 # Technical Architecture Document (stack, components, NFRs, risks)
+    └── working-spec.md        # Working Specification (functional requirements, actors, assumptions)
+```
+
+---
+
+## Architecture Notes
+
+This repo documents the architecture of a small self-contained REST API. Key decisions for implementers:
+
+**Stack** (from `architecture/tad.md`):
+- Runtime: Node.js LTS ≥ 20
+- Language: TypeScript strict mode, compiled to ES2020+, output to `dist/`
+- Framework: Express.js v4 or v5
+- Testing: Jest + `ts-jest` or Vitest (choice left to implementer)
+- Linting: ESLint with `@typescript-eslint` ruleset
+
+**Component layout** for the implementation repo:
+| File | Responsibility |
+|---|---|
+| `server.ts` | Entry point; creates Express app, registers middleware, listens on `process.env.PORT \|\| 3000` |
+| `routes/quotes.ts` | All four REST routes: `GET /health`, `GET /quote`, `GET /quotes`, `POST /quotes` |
+| `store.ts` | In-memory quote repository — `getAll()`, `getRandom()`, `add(quote)`; seeded with 5 quotes at startup |
+| `validation.ts` | Pure, side-effect-free functions that validate request bodies; return typed `Quote` or error string |
+| `middleware/error.ts` | Four-argument Express error handler; logs server-side, returns `{ error: "Internal server error" }` on HTTP 500 — never leaks stack traces |
+
+**Data model**:
+```
+Quote { text: string, author: string }
+```
+No ID field in v1. In-memory store only — data resets on restart by design.
+
+**Key design constraints** (from `architecture/working-spec.md`):
+- No persistence, no database, no external integrations
+- No authentication — all endpoints publicly accessible
+- No pagination — `GET /quotes` returns full list
+- No rate limiting
+- Single process; `GET /health` is the liveness probe endpoint
+
+---
+
+## Code Style
+
+Applies to the **implementation repo** (not this docs repo):
+
+- **TypeScript**: `strict: true`, `target: "ES2020"` in `tsconfig.json`
+- **Linting**: ESLint with `@typescript-eslint` rules; `npm run lint` must exit cleanly — zero warnings on committed code
+- **Validation**: Input validation logic lives in `validation.ts` as pure functions, called by route handlers before any store mutation
+- **Responses**: All responses use `res.json(...)` and return `application/json`
+- **Error responses**: 400 errors include a human-readable `error` field; 500 errors return `{ error: "Internal server error" }` only