fix(logging): record metadata values that were silently dropped

[bmc08gt]

MetadataBuilder declared infix fun String.to(value: Any). A non-null parameter makes the member inapplicable to a nullable argument, so the call resolves to kotlin.to instead, builds a Pair and discards it in statement position. The field never reaches the log. It compiles clean and produces at most an unused-expression warning, so nothing flagged it.

The declared type is what breaks it, not the runtime value. A String? holding "hello" was dropped just as silently as one holding null.

The fix

Adding an Any? overload alongside the existing Any is not possible — both erase to to(String, Object)V, and Kotlin rejects the platform declaration clash. The single member is widened to Any? instead, recording NULL_PLACEHOLDER for a null. That keeps it the only applicable candidate, so kotlin.to can no longer win for any String key.

Audit

kotlin.to was temporarily shadowed inside the builder with a @Deprecated candidate, which makes exactly the fallback call sites diagnose while leaving correct ones silent. Compiling every module's main and unit-test sources found eight sites dropping fields:

Site	Fields
NotificationService	title, body
CoinbaseOnRampController	correlationId, responseBody, errorLink
GooglePlayBillingClient	purchases
SwapViewModel	errorMessage
RealVerifiedFiatCalculator	balance quarks

Each is now explicit at the call site rather than leaning on the placeholder, so an absent value reads as what the field means: -1 for a count, "none" for an amount, "" where the file already used orEmpty.

What is not recorded

These traces reach breadcrumb sinks for every TraceType except Silent, so unmasking a dropped field can start sending content to Bugsnag that was previously discarded by accident.

Push content stays out: title and body become the derived silent and has_body. The Coinbase responseBody is kept, matching the sibling path in the same file — the error envelope is a fixed schema of correlationId, errorType, errorLink, code and message, and it is most useful exactly when parse() returns null.

The second commit is a separate leak the audit surfaced rather than a nullability bug. GiftCardFundingWorker recorded giftCard.entropy — mnemonic.getBase58EncodedEntropy(), the seed controlling the gift card's funds — in both funding traces. It is non-null, so it was reaching Bugsnag on every success and failure. It now logs the vault public key, which identifies the same account and is already public on-chain.

Tests

MetadataBuilderTest covers a String? holding a value and one holding null, plus nullable non-String types. Five of its seven tests fail if the parameter is narrowed back to Any.