Add CLAUDE file (#7)

Author: trevor-e

CLAUDE.md

@@ -0,0 +1,85 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## What is This?
+
+Livegrep is a tool for interactive regex search of large source repositories, inspired by Google Code Search. This is Sentry's fork of [livegrep/livegrep](https://github.com/livegrep/livegrep).
+
+Two-process architecture:
+- **codesearch** (C++): Builds index from git repos/filesystem, serves search over gRPC (port 9999)
+- **livegrep** (Go): Stateless HTTP frontend connecting to codesearch, serves web UI (port 8910)
+
+The web UI uses Backbone.js/jQuery with PrismJS for syntax highlighting, bundled via webpack.
+
+## Build System
+
+Uses **Bazel** (v7.6.0 pinned in `.bazelversion`). Install via [bazelisk](https://bazel.build/install/bazelisk).
+
+```bash
+# Build everything
+bazel build //...
+
+# Build specific targets
+bazel build //src/tools:codesearch    # C++ backend
+bazel build //cmd/livegrep:livegrep   # Go frontend
+```
+
+A convenience Makefile wraps common workflows:
+
+```bash
+make build       # Build both backend and frontend
+make index       # Build search index (uses doc/examples/livegrep/index.json)
+make run         # Build and start both services
+make stop        # Stop all services
+make status      # Check if services are running
+make logs-backend / make logs-web
+```
+
+## Testing
+
+```bash
+bazel test //...                       # Run all tests
+bazel test --test_arg=-test.v //...    # Verbose (used in CI)
+```
+
+- C++ tests: `test/` directory (googletest) — `codesearch_test`, `planner_test`, `tagsearch_test`
+- Go tests: `server/` directory — `query_test.go`, `server_test.go`, `fileview_test.go`
+
+## Formatting
+
+Go code must pass `gofmt`. CI checks this:
+```bash
+bazel run @rules_go//go -- fmt ./...
+```
+
+## Key Directories
+
+| Directory | Language | Role |
+|-----------|----------|------|
+| `src/` | C++ | Search engine core, indexer, gRPC server |
+| `src/proto/` | Protobuf | gRPC service + index config schemas |
+| `server/` | Go | HTTP frontend, gRPC client, templates |
+| `cmd/` | Go | Binary entrypoints (livegrep, reindexers, CLI) |
+| `web/` | JS/HTML/CSS | Frontend UI (webpack, Backbone.js, PrismJS) |
+| `third_party/` | C++ | Vendored deps (divsufsort, utf8cpp) |
+
+## Configuration
+
+- **Index config** (codesearch): JSON following `src/proto/config.proto` schema. Example: `doc/examples/livegrep/index.json`
+- **Server config** (livegrep frontend): JSON following `server/config/config.go`. Example: `doc/examples/livegrep/server.json`
+  - `file_ext_to_lang`: Maps file extensions to PrismJS language names for syntax highlighting
+  - `file_first_line_regex_to_lang`: Detects language by shebang/first line
+
+## Sentry Fork Additions
+
+- **Test file deranking**: Results from test files are sorted to the end of search results (`server/api.go:isTestFile`)
+- **Syntax highlighting**: PrismJS-based highlighting in search results (`web/src/codesearch/highlight.js`)
+- **Healthcheck age limit**: Backend healthcheck fails if index > 3.5 hours old (`server/server.go:MaxIndexAge`)
+
+## Go + Bazel Notes
+
+- Go IDE support requires the gopackagesdriver (configured in `.vscode/settings.json` for VSCode)
+- Go module path: `github.com/livegrep/livegrep`
+- Protobuf Go bindings are at `src/proto/go_proto`
+- To update Go deps: edit `go.mod`, then regenerate Bazel targets with gazelle