reorganize: consolidate demo directories

- Consolidate _demo, _pydemo, _embdemo into single _demo directory structure
- Organize demos by language: _demo/{go,py,c,embed}/
- Categorize demos based on imports:
- Python library demos (py imports) → _demo/py/
- C/C++ library demos (c/cpp imports) → _demo/c/
- Go-specific demos → _demo/go/
- Embedded demos → _demo/embed/
- Move C-related demos (asm*, cabi*, cgo*, linkname, targetsbuild) from go/ to c/
- Update all path references in README.md and GitHub workflows
- Improve demo organization and navigation as requested in #1256

🤖 Generated with [Claude Code](https://claude.ai/code)

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

_demo/c/llama2-c/run.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"github.com/goplus/lib/c"
+	"github.com/goplus/lib/c/llama2"
+	"github.com/goplus/lib/c/time"
+)
+
+func main() {
+	var prompt *c.Char = c.Str("Once upon a time")
+	var checkpointPath *c.Char = c.Str("stories15M.bin")
+	var tokenizerPath *c.Char = c.Str("tokenizer.bin")
+	var temperature, topp c.Float = 1.0, 0.9
+	var steps c.Int = 256
+	var rngSeed uint64 = uint64(time.Time(nil))
+
+loop: // parse command line arguments
+	for {
+		switch c.Getopt(c.Argc, c.Argv, c.Str("m:")) {
+		case 'm':
+			checkpointPath = c.Optarg
+			c.Fprintf(c.Stderr, c.Str("==> use model: %s\n"), checkpointPath)
+		case -1:
+			break loop
+		}
+	}
+	if c.Optind < c.Argc {
+		prompt = c.Index(c.Argv, c.Optind)
+		c.Fprintf(c.Stderr, c.Str("==> prompt: %s\n"), prompt)
+	}
+
+	// build the Transformer via the model .bin file
+	var transformer llama2.Transformer
+	llama2.BuildTransformer(&transformer, checkpointPath)
+
+	// build the Tokenizer via the tokenizer .bin file
+	var tokenizer llama2.Tokenizer
+	llama2.BuildTokenizer(&tokenizer, tokenizerPath, transformer.Config.VocabSize)
+	// build the Sampler
+	var sampler llama2.Sampler
+	llama2.BuildSampler(&sampler, transformer.Config.VocabSize, temperature, topp, rngSeed)
+
+	// run!
+	llama2.Generate(&transformer, &tokenizer, &sampler, prompt, steps)
+
+	// memory and file handles cleanup
+	llama2.FreeSampler(&sampler)
+	llama2.FreeTokenizer(&tokenizer)
+	llama2.FreeTransformer(&transformer)
+}