Assume zero decimals for assets without metadata (e.g. control asset)

[gringokiwi]

We appear to be assuming that the decimal precision of an asset is 8 if unset.

[arkanaai]

Codebase Analysis

Where the bug lives

The default of 8 is baked in at two levels:

1. Core conversion functions ():

// Line 6
decimals = decimals ?? 8  // unitsToCents
// Line 11
decimals = decimals ?? 8  // centsToUnits

These are the root cause — everything that passes undefined decimals silently gets 8.

2. Every call-site that propagates undefined (all use ?? 8 as inline fallback):

• src/screens/Apps/Assets/Detail.tsx:69 — meta?.decimals ?? 8
• src/screens/Apps/Assets/Reissue.tsx:39, Burn.tsx:38, MintSuccess.tsx:24, Index.tsx:70
• src/screens/Wallet/Send/Form.tsx:156, 218, 507, Send/Details.tsx:204, Send/Success.tsx:37
• src/screens/Wallet/Transaction.tsx:158, src/components/TransactionsList.tsx:96
• src/screens/Settings/Vtxos.tsx:256, src/components/AssetCard.tsx:33

The control asset is already handled correctly in one place — Mint.tsx:112 hard-codes { decimals: 0 } — but that metadata never reaches the display paths above.

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Acceptance criteria

• unitsToCents / centsToUnits in assets.ts default to 0 decimals, not 8, when decimals is undefined
• All inline ?? 8 fallbacks across screens/components are updated to ?? 0
• Control assets (assets with no metadata or metadata with no decimals field) display integer amounts with no decimal shift
• Bitcoin/sats amounts are unaffected — callers that handle BTC must explicitly pass decimals: 8, not rely on the default
• Existing unit tests for unitsToCents / centsToUnits updated; add a test for the undefined-decimals case

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Suggested approach

1. Change the two defaults in src/lib/assets.ts from ?? 8 → ?? 0.
2. Grep for ?? 8 across the repo and update each to ?? 0 (or remove the fallback if the caller already passes explicit decimals).
3. Verify that BTC callers always pass an explicit 8 — none should be relying on the default.
4. Smoke-test: send/receive a control asset, verify amounts display as whole integers.

[tiero]

Let's Always default to 0 decimals please @Kukks better to overshoot sending way less than way more

[gringokiwi]

@bordalix you got this or do you want me to have a crack?