epic: New Thread Settings Panel with correct file overwrites

[0xSage]

Motivation

• Right panel was missing params / sub sections
• UI was confusing, because even though Right Panel edits affect thread.json only, users felt like they were editting model.json, assistant.json

Designs

https://www.figma.com/file/ytn1nRZ17FUmJHTlhmZB9f/Jan-App?type=design&node-id=112-37497&mode=design&t=s5Td4SkT9LRH86bS-0

Stories

1. Users can edit all of the parameters in thread.json except the following:

• id: show but gray out
• object: dont show in UI
• assistants[0] > defaults to Jan (obv this can't be editted)
• assistants[0].assistant_id: don't show in UI
• created: don't show in UI
• updated: don't show in UI
• metadata: don't show in UI

This might deviate a bit from what's rendered in designs, please follow this guide

2. Users can refine model configs in the following sections, with changes affecting thread.json

• Inference parameters
• Model parameters
• engine parameters

3. Remove autosave. Users must click save button.

4. Basic error handling around users not saving changes in Thread Settings

5. When users edit the following sections, button must say "save & reload" because it requires models to be reloaded at nitro level. Otherwise, button just says "save"

• Model params
• Engine params

6. Sections have tooltips:

• Do your best to put in placeholder
• @tikikun @hahuyhoang411 for the final copy during QA

7. Change the Assistant & Model section Dropdowns to "edit global defaults for [model/assistant name]" rather than what we had before. See designs.

8. If users edit assistant.json, or model.json directly, the overwrites take effect for subsequent new threads

• #1203 : assistant default params should be changeable via file
• Same for model.json
• When properties are undefined, they follow inheritance rule: thread inherits assistant.json, inherits model.json

Tasklist

• [x] https://github.com/janhq/internal/issues/66
• [ ] #1212
• [x] #1190 (quick UI fix, though may not be relevant anymore bc you guys want to allow mid-thread model switching?)
• [ ] #1129 @hieu-jan
• [x] #1189 (Needs a decision: won't fix, sort alphabetically within section, reference default model.jsons, etc. Up to app pod.
• [x] #1183
• [x] #1250 @urmauur

Not in Scope

• #1175
• Possibly #1189 if the decision is won't fix
• Feel free to drag other tasks here.