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This allows building:
-  only `mistral.rs` engine: `--no-default-features --features mistralrs`  
- or only `llama.cpp` engine: `--no-default-features --features llamacpp`. 

Since llama.cpp became a default we'd only tested building both at once. The docs already said we supported that but there was some combo of Rust features that didn't build. This is the fix.

It was confusing to have two names for one type.

This tidy up started in #1064 , is now complete.

Unify them with all our other logs, so we can filter with DYN_LOG, they will eventually go to the log aggregation, etc.

Previously `mistral.rs` was the default engine for both safetensors and GGUF models. Now it is only the default for safetensors, `llama.cpp` becomes the default for GGUF.

Why?

- Since #1177 `llama.cpp` is built-in by default, so we can switch.
- `llama.cpp` is very very good at running GGUF (but can't run other types of model), so we should switch.

Dynamo's multi-engine support gives us a secret super-power: we can use the best engine for this specific format or model.

We can still run GGUF with mistralrs by doing `out=mistralrs`.

This change corrects the README.md file in the examples/multimodal folder:
- Correct "vllm worker" to "decode worker"
- Correct assertion that data is moved via NATS when embeddings are moved via RDMA.

Additionally, this change updates the textual graphs with Mermaid graphs for improved presentation on github.com.

- Add Granite to our tokenizer
- Fix pre-processor to load context length correctly
- Add strftime_now Jinja function for prompt templates
- Update llama.cpp
- Handle trtllm errors when not using trtllm

Support depends on the engine:

- `mistral.rs`, our default engine, doesn't support Granite yet.

- `llama.cpp` does and works very well:
```
dynamo-run out=llamacpp ~/llms/granite-3.3-2b-instruct-Q4_K_M.gguf --context-length 16384
```

- `vllm` also works very well:
```
dynamo-run in=http out=vllm ~/llms/granite-3.3-2b-instruct --context-length 16384
```

- `sglang` mostly works, but it doesn't catch the stop token, so we do in the HTTP ingress, and log an error. The Text ingress doesn't catch it because I disabled it to make the raw echo engine work. A bit of work to do here.

Closes: #1245 

Signed-off-by: Hongkuan Zhou <tedzhouhk@gmail.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>