refactor(tinygrad): reuse tinygrad.apps.llm instead of vendored Transformer

[mudler]

Drop the 295-line vendor/llama.py fork in favor of tinygrad.apps.llm, which now provides the Transformer blocks, GGUF loader (incl. Q4/Q6/Q8 quantization), KV-cache and generate loop we were maintaining ourselves.

What changed:

• New vendor/appsllm_adapter.py (~90 LOC) — HF -> GGUF-native state-dict keymap, Transformer kwargs builder, _embed_hidden helper, and a hard rejection of qkv_bias models (Qwen2 / 2.5 are no longer supported; the apps.llm Transformer ties bias=False on Q/K/V projections).
• backend.py routes both safetensors and GGUF paths through apps.llm.Transformer. Generation now delegates to its (greedy-only) generate(); Temperature / TopK / TopP / RepetitionPenalty are still accepted on the wire but ignored — documented in the module docstring.
• Jinja chat render now passes enable_thinking=False so Qwen3's reasoning preamble doesn't eat the tool-call token budget on small models.
• Embedding path uses _embed_hidden (block stack + output_norm) rather than the custom embed() method we were carrying on the vendored Transformer.
• test.py gains TestAppsLLMAdapter covering the keymap rename, tied embedding fallback, unknown-key skipping, and qkv_bias rejection.
• Makefile fixtures move from Qwen/Qwen2.5-0.5B-Instruct to Qwen/Qwen3-0.6B (apps.llm-compatible) and tool_parser from qwen3_xml to hermes (the HF chat template emits hermes-style JSON tool calls).

Verified with the docker-backed targets:
test-extra-backend-tinygrad 5/5 PASS
test-extra-backend-tinygrad-embeddings 3/3 PASS
test-extra-backend-tinygrad-whisper 4/4 PASS
test-extra-backend-tinygrad-sd 3/3 PASS

Description

This PR fixes #

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