allow model specifier in t3 bang commands

[teaonrocks]

Description

Previously, using !t3 in Unduck always routed your query through the most recently-used T3 model. This change allows you to pin a specific model on the fly by appending @ to the bang. For example:

• !t3@o4m what’s the weather? → uses the o4-mini model
• !t3@g25f summarize this… → uses the gemini 2.5 flash model
  If no suffix is provided (!t3 foo), it still falls back to your default model stored in localStorage (or gemini 2.5 flash, if none is configured).

changes:

src/main.ts:

• change regex for match to stop where there is an "@"
• add a t3match regex to get the specified model
• store matched url in a variable so that it can be overwritten if there is a specified model

added:

src/t3bangs.ts

• all the recommended models in t3chat