chore: add CLAUDE.md (#398)

## Summary

Add CLAUDE.md

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## Are there any deployment considerations?

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: adds documentation only and does not change runtime code,
build outputs, or CI behavior.
> 
> **Overview**
> Adds `CLAUDE.md`, a repo-specific contributor guide covering the
monorepo overview, common Yarn/Turbo commands (build/test/lint/publish),
package layout and key `highlight.run` entry points, CI workflow notes,
and E2E testing guidance (including cross-origin iframe recording
troubleshooting).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
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<!-- /CURSOR_SUMMARY -->

Author: Vadman97

CLAUDE.md

@@ -0,0 +1,143 @@
+# CLAUDE.md
+
+## Overview
+
+LaunchDarkly Observability SDK monorepo. Contains browser, Node.js, mobile, and backend SDKs for session replay, error monitoring, logging, and distributed tracing. Fork of highlight.io.
+
+**Package manager:** Yarn 4.9.1 (`yarn install`)
+**Build system:** Turborepo
+**rrweb:** Git submodule at `rrweb/` - run `git submodule update --init --recursive` after clone (the preinstall hook handles this automatically).
+
+## Key Commands
+
+```bash
+yarn install              # Install all dependencies
+yarn build                # Build all packages (excludes rrweb, nextjs)
+yarn build:sdk            # Build only @launchdarkly/* + highlight.run
+yarn test                 # Build, lint, enforce-size, then test all packages
+yarn format-check         # Check formatting (prettier)
+yarn format:all           # Fix formatting
+yarn lint                 # Lint all packages
+yarn enforce-size         # Check bundle size limits (256KB brotli)
+yarn docs                 # Generate TypeDoc documentation
+```
+
+### Filtering to specific packages
+
+```bash
+yarn turbo run build --filter @launchdarkly/observability
+yarn turbo run test --filter highlight.run
+yarn turbo run build --filter '@launchdarkly/*'
+```
+
+### Publishing (CI-only, runs on main)
+
+```bash
+yarn publish              # @launchdarkly/* packages
+yarn publish:highlight    # highlight.run + @highlight-run/* packages
+```
+
+## Package Structure
+
+### LaunchDarkly SDKs (`sdk/@launchdarkly/`)
+
+| Package | Description |
+|---------|-------------|
+| `observability` | Browser SDK - errors, logs, traces |
+| `session-replay` | Browser SDK - session replay (thin wrapper over highlight.run) |
+| `observability-shared` | Internal shared types and GraphQL codegen (private) |
+| `observability-node` | Node.js SDK |
+| `observability-react-native` | React Native SDK |
+| `react-native-ld-session-replay` | React Native session replay |
+| `observability-python` | Python SDK |
+| `observability-dotnet` | .NET SDK |
+| `observability-android` | Android SDK |
+| `observability-java` | Java SDK |
+
+### Core packages
+
+| Package | Description |
+|---------|-------------|
+| `sdk/highlight-run` | Core browser library - session replay + observability. Most logic lives here. |
+| `rrweb/` | Forked session replay recording library (git submodule, ~15 sub-packages) |
+| `go/` | Go observability SDK |
+
+### Key source files in highlight.run
+
+- `src/index.tsx` - Public API, `H` global singleton
+- `src/sdk/record.ts` - `RecordSDK` class (session replay recording logic)
+- `src/sdk/LDRecord.ts` - `LDRecord` global singleton (LaunchDarkly entry point)
+- `src/client/index.tsx` - `Highlight` class (underlying implementation)
+- `src/client/workers/highlight-client-worker.ts` - Web Worker for async data upload
+- `src/client/types/record.ts` - `RecordOptions` type definition
+- `src/client/types/iframe.ts` - Cross-origin iframe protocol types
+- `src/client/constants/sessions.ts` - Timing constants (`FIRST_SEND_FREQUENCY`, etc.)
+- `src/plugins/record.ts` - LaunchDarkly plugin interface (`LDPlugin`)
+
+### Default backend URL
+
+The SDK sends data to `https://pub.observability.app.launchdarkly.com` by default. Configurable via `backendUrl` option.
+
+## Code Style
+
+**Prettier config** (`.prettierrc`): Tabs, no semicolons, single quotes, trailing commas, 80 char width.
+
+**Pre-commit hook** (husky): Runs `pretty-quick --staged` automatically.
+
+**TypeScript**: Strict mode. All browser SDKs build with Vite (ESM + UMD). Node SDKs use rollup or tsc.
+
+**Bundle size**: All browser packages enforce 256KB brotli limit via `size-limit`. Check with `yarn enforce-size`.
+
+## CI Pipeline
+
+The main workflow is `.github/workflows/turbo.yml` (runs on push to main and PRs):
+1. `yarn install`
+2. `yarn dedupe --check`
+3. `yarn format-check`
+4. `yarn test` (which runs build -> lint -> enforce-size -> test)
+5. On main: publishes to npm
+
+Other workflows handle language-specific SDKs (Go, Python, .NET, Android, Java, Ruby, Rust, Elixir) and E2E tests.
+
+Releases are managed by `release-please` - version bumps happen automatically via PR.
+
+## E2E Tests
+
+### Framework examples (`e2e/`)
+
+Example apps for testing SDK integrations: React, Next.js, Angular, Express, NestJS, Remix, Hono, Cloudflare Worker, React Native, Go, Python, .NET, Ruby, and more.
+
+```bash
+# Run via docker compose
+cd e2e
+docker compose build sdk && docker compose build base
+docker compose build <example> && docker compose up <example>
+
+# Run specific frameworks via turbo
+yarn e2e:nextjs
+yarn e2e:express
+yarn e2e:cloudflare
+```
+
+### Pytest E2E (`e2e/tests/`)
+
+Python-based tests that start apps, make requests, and validate data appears in the backend via GraphQL queries. Uses `app_runner.py` for lifecycle management with health check polling.
+
+```bash
+cd e2e/tests
+poetry install
+poetry run python src/app_runner.py <example>
+poetry run pytest
+```
+
+**Run tests:**
+```bash
+# Diagnose live customer URLs (headed browser, slow-mo for observation)
+yarn test:live
+
+# Run local reproduction tests (headless, uses local Express servers on :3001/:3002)
+yarn test:local
+
+# Run everything
+yarn test
+```