…-token UX from UAT issues cp-7.73.0 (#28302)

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## **Description**

Addresses several UAT issues in the Predict buy-with-any-token flow:

- **Auto-select best payment token**: New
`usePredictDefaultPaymentToken` hook auto-selects the token with the
highest fiat balance when Predict balance is below MINIMUM_BET ($1),
instead of requiring manual selection. Resets to Predict balance when
sufficient.
- **Optimistic positions on deposit**: Creates optimistic positions from
the order preview at deposit time so the position appears immediately in
the portfolio while the deposit confirms. Clears optimistic positions on
failure (both direct order failures and failed deposit-and-order
transactions).
- **Navigate back on deposit**: Navigate back when the deposit-and-order
flow begins, so the user isn't stuck on the buy form.
- **Keep token selection always enabled**: Removes the `canSelectToken`
gate — the pay-with-token row is now always interactive (disabled only
while placing an order).
- **"Predict balance first" hint**: Shows "Your Predict balance will be
used first" below the pay-with row when an external token is selected,
so users understand the payment order.
- **Deposit amount guards**: `depositAmount` now returns 0 when the
preview is unavailable or the bet is below minimum, preventing premature
deposit calculations and stale values from triggering the deposit flow.
- **Updated insufficient funds messaging**: Error messages now suggest
trying a different token when funds are insufficient.
- **Fix text overflow on Polymarket terms**: Nests the "learn more" link
inside the disclaimer text and adds horizontal padding to prevent
overflow.
- **Fix premature payment token reset**: Adds a
`totalPayForPredictBalance > 0` guard so the auto-reset effect only
fires when there is an actual bet amount, preventing the selected token
from being cleared immediately after selection.
- **Depositing toast notification**: Shows a "Prediction in progress"
toast with spinner when the deposit phase begins and invalidates
position queries to reflect the optimistic position.


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## **Changelog**

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## **Related issues**

Fixes:

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

## **Screenshots/Recordings**

https://www.loom.com/share/c25681fd77a444e496f999a23a55b0e6

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before and after of your change. -->

### **Before**

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### **After**

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## **Pre-merge author checklist**

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I've included tests if applicable
- [ ] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Updates buy-with-any-token order state transitions, optimistic
position caching, and navigation/toast behavior; mistakes could cause
incorrect UI state or stale/phantom positions during deposit/order
failures.
> 
> **Overview**
> Improves the *buy-with-any-token* flow by introducing a new `order`
event status `depositing` and publishing it when the flow transitions
into the deposit phase, with a matching “Prediction in progress” toast
and positions query invalidation.
> 
> Adds preview-based **optimistic positions** during deposit via
`PolymarketProvider.createOptimisticPositionFromPreview`, and ensures
cleanup via `clearOptimisticPosition` when `placeOrder` fails or when a
`depositAndOrder` transaction fails.
> 
> Refines buy screen UX: auto-selects a default payment token when
Predict balance is below `MINIMUM_BET` (new
`usePredictDefaultPaymentToken`), removes the `canSelectToken` gate (row
only disabled while placing), navigates back when entering `DEPOSITING`,
adds a “Predict balance will be used first” hint, guards deposit amount
calculation until fees/minimum bet are available, and updates
insufficient-funds copy to suggest trying another token; also adjusts
the Polymarket TOS disclaimer layout to prevent overflow.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
7f97218. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->