chore: add CLAUDE.md with project guidance for Claude Code

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

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+litenote-jetstream is the backend for Litenote, a blogging platform built on the AT Protocol (Bluesky ecosystem). It has two processes:
+
+1. **Jetstream listener** (`jetstream.ts`) — Subscribes to the AT Protocol firehose via `@skyware/jetstream`, filtering for `space.litenote.note` records. On create/update events, it upserts notes into a local SQLite database.
+2. **HTTP API server** (`server.ts`) — An Oak (Deno HTTP framework) server on port 8080 that exposes read-only endpoints to query stored notes.
+
+Both processes share the same SQLite database (`src/data/db.ts`).
+
+## Commands
+
+```bash
+# Run jetstream listener (dev, with watch)
+deno task jetstream
+
+# Run API server (dev, with watch)
+deno task server
+
+# Run both for production (as in Docker)
+deno task jetstream:prod & deno task server:prod
+
+# Run database migration
+deno task migrate
+
+# Lint
+deno lint
+
+# Format
+deno fmt
+```
+
+## Architecture
+
+- **Runtime**: Deno (not Bun, despite the README). Uses `deno.json` for task definitions and import maps.
+- **Database**: SQLite via `https://deno.land/x/sqlite/mod.ts`. DB path is configurable via `SQLITE_PATH` env var, defaults to `notes.db`.
+- **Note schema**: Defined as an AT Protocol lexicon in `lexicons/space/litenote/note.json`. Notes have `title`, `content` (markdown), optional `images` (blob refs), `publishedAt`, and `createdAt`. Primary key is `(did, rkey)`.
+- **API endpoints**:
+  - `GET /notes?cursor=&limit=` — paginated notes (all users)
+  - `GET /:did/notes?cursor=&limit=` — paginated notes for a specific DID
+- **Pagination**: cursor-based using `rkey`, descending order.