webui: add OAI-Compat Harmony tool-call streaming visualization and persistence in chat UI

[ServeurpersoCom]

- Purely visual and diagnostic change, no effect on model context, prompt
  construction, or inference behavior

- Captured assistant tool call payloads during streaming and non-streaming
  completions, and persisted them in chat state and storage for downstream use

- Exposed parsed tool call labels beneath the assistant's model info line
  with graceful fallback when parsing fails

- Added tool call badges beneath assistant responses that expose JSON tooltips
  and copy their payloads when clicked, matching the existing model badge styling

- Added a user-facing setting to toggle tool call visibility to the Developer
  settings section directly under the model selector option

Close #16597

[ServeurpersoCom]

I have to do a little cleaning, the patch was not merged properly on my side. -> draft

[ServeurpersoCom]

This PR is now clean, but it was developed after this one: #16562

[allozaur]

Alright, @ServeurpersoCom, let's move forward with this one after merging #16562 ;) Let me know when you've addressed the merge conflicts and I'll gladly review the code

[ServeurpersoCom]

For the tool call inspector, do you prefer having one spoiler block per tool call, or a single aggregated spoiler wrapping all tool calls in the message?

It's rebased/reworked now. I push --force :)

[ServeurpersoCom]

Feel free to dissect the architecture as deep as you want! Component boundaries, store coupling, service layering, anything that smells non-idiomatic.
Also, if we end up polishing this feature further, I’m thinking it could live in a dedicated module for cleaner boundaries ?

lib/
 └─ toolcalls/
     ├─ toolcall-service.ts
     ├─ toolcall-store.ts
     ├─ ToolCallBlock.svelte
     └─ ToolCallItem.svelte

[ServeurpersoCom]

And we could even imagine the architecture being reusable later : like having a small JavaScript execution module decoupled from the UI, so the model could actually interact with a JS thread it coded itself.
That would also cover, in a more generic way, the proposal from PR #13501 by @samolego but in this case, the model would generate and run its own JS tools. Done properly, it’s no more of a security risk than the HTML/JS preview you get in Hugging Face Chat or Claude!

[ServeurpersoCom]

Includes a very small optimization from the previous PR (scroll listener removal). It landed here intentionally :D

[ServeurpersoCom]

Testing :

Add this

{
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "simple_addition_tool",
        "description": "A dummy calculator tool used for testing multi-argument tool call streaming.",
        "parameters": {
          "type": "object",
          "properties": {
            "a": {
              "type": "number",
              "description": "The first number to add."
            },
            "b": {
              "type": "number",
              "description": "The second number to add."
            }
          },
          "required": ["a", "b"]
        }
      }
    }
  ]
}

Here :

And ask model :