feat(tui): make dialog keybinds configurable (#6143)

[CasualDeveloper]

Summary

• Add configurable keybinds for dialog actions (delete, rename, favorite, etc.)
• Change session_rename default from none to ctrl+r

Closes #6143

New Keybind Options

Option	Default	Description
session_delete	ctrl+d	Delete session
session_rename	ctrl+r	Rename session
stash_delete	ctrl+d	Delete stash entry
model_provider_list	ctrl+a	Open provider list
model_favorite_toggle	ctrl+f	Toggle model favorite

Usage

{
  "keybinds": {
    "session_delete": "super+d",
    "session_rename": "super+r"
  }
}

Note: If another PR touching packages/sdk/openapi.json merges first, rebase and rerun bun ./script/generate.ts, then update packages/sdk/js/src/v2/gen/types.gen.ts.