Build and run for embeded

doc/Embedded_Cmd.md

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+# LLGo Embedded Development Command Line Options
+
+## Flags
+
+- `-o <file>` - Specify output file name
+- `-target <platform>` - Specify target platform for cross-compilation
+- `-file-format <format>` - Convert to specified format (**requires `-target`**)
+  - Supported: `elf` (default), `bin`, `hex`, `uf2`, `zip`, `img`
+- `-emulator` - Run using emulator (auto-detects required format)
+- `-d <device>` - Target device for flashing or testing
+
+## Commands
+
+### llgo build
+Compile program to output file.
+- No `-target`: Native executable
+- With `-target`: ELF executable (or `-file-format` if specified)
+
+### llgo run  
+Compile and run program.
+- No `-target`: Run locally
+- With `-target`: Run on device or emulator
+
+### llgo test
+Compile and run tests.
+- No `-target`: Run tests locally
+- With `-target`: Run tests on device or emulator
+- Supports `-emulator` and `-d` flags
+
+### llgo install
+Install program or flash to device.
+- No `-target`: Install to `$GOPATH/bin`
+- With `-target`: Flash to device (use `-d` to specify device)
+
+## Examples
+
+```bash
+# Native development
+llgo build hello.go                              # -> hello
+llgo build -o myapp hello.go                     # -> myapp
+llgo run hello.go                                # run locally
+llgo install hello.go                            # install to bin
+
+# Cross-compilation
+llgo build -target esp32 hello.go                # -> hello (ELF)
+llgo build -target esp32 -file-format bin hello.go  # -> hello.bin
+llgo run -target esp32 hello.go                  # run on ESP32
+llgo run -target esp32 -emulator hello.go        # run in emulator
+llgo test -target esp32 -d /dev/ttyUSB0          # run tests on device
+llgo test -target esp32 -emulator                # run tests in emulator
+llgo install -target esp32 -d /dev/ttyUSB0 hello.go  # flash to specific device
+```