add CLAUDE.md with build, CLI, and lifecycle documentation

CLAUDE.md

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+# CLAUDE.md — gost/
+
+CLI binary entry point for GOST (GO Simple Tunnel). This module compiles the `gost` command.
+
+## Build & Run
+
+```bash
+cd gost && go build ./cmd/gost/...
+
+# Cross-compile
+CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" ./cmd/gost/...
+
+# Build all platforms
+make all
+
+# Run
+./gost -L "http://:8080" -F "socks5://:1080"
+./gost -C gost.yml
+```
+
+## Structure
+
+| File | Purpose |
+|------|---------|
+| `cmd/gost/main.go` | CLI entry point: flag parsing, multi-worker mode (`--` separator), program launch via `svc.Run` |
+| `cmd/gost/program.go` | Service lifecycle (`Init`/`Start`/`Stop`), config loading, API/metrics/profiling servers, SIGHUP reload |
+| `cmd/gost/register.go` | Blank imports for all built-in handlers, listeners, dialers, connectors — triggers `init()` registration |
+| `cmd/gost/version.go` | Version string (`3.3.0`) |
+
+## CLI Flags
+
+| Flag | Usage |
+|------|-------|
+| `-L` | Inline service definition (repeatable) |
+| `-F` | Inline chain node definition (repeatable) |
+| `-C` | Path to config file (YAML/JSON) |
+| `-D` / `-DD` | Debug / trace logging |
+| `-api` | API service address (e.g. `:8080`) |
+| `-metrics` | Prometheus metrics address |
+| `-O` | Output merged config as yaml or json, then exit |
+| `-V` | Print version and exit |
+
+## Multi-Worker Mode
+
+Arguments separated by ` -- ` spawn multiple worker processes via `exec.CommandContext`. Each worker runs as a child process with `_GOST_ID` set. Any worker's exit cancels all others. This is triggered in `init()` before flag parsing.
+
+## Service Lifecycle
+
+- `Init` → calls `parser.Init()` with all CLI/config inputs
+- `Start` → `parser.Parse()` → `loader.Load()` → `p.run()` (starts services, API, metrics, profiling)
+- `Stop` → cancels reload context, closes all services
+- SIGHUP → `reloadConfig()` re-parses and re-runs without restarting the process
+
+## Key Dependencies
+
+- `github.com/go-gost/core` — interface definitions
+- `github.com/go-gost/x` — all implementations, config, registry
+- `github.com/judwhite/go-svc` — OS service framework (handles daemon/SIGHUP/SIGTERM)
+
+## Registration Pattern
+
+All components register via `init()` side-effects in their packages. `cmd/gost/register.go` triggers them with blank imports. When adding a new built-in handler/listener/dialer/connector, add a blank import here.
+
+## Tests
+
+Tests are in `tests/e2e/` — integration tests using the built binary. No unit tests. Run with `go test ./tests/e2e/...`.