`.networkConnectionLost` is classified as `DeviceIsOfflineError` even when the server severed the connection

> Split out from Automattic/wordpress-rs#1497 — *Swift executor URLSession error audit*. Section A — Converted to the wrong Rust error.
>
> File references are to `native/swift/Sources/wordpress-api/SafeRequestExecutor.swift` unless noted; `:NNN` line numbers were verified against `fix/converge-executor-error-classification`.

**Severity: high.** Apple documents -1005 as "a client or server connection was severed in the middle of an in-progress load" — it fires for server/proxy RSTs, load-balancer idle timeouts, and the notorious iOS stale keep-alive reuse case, with the device fully online. Apps show offline banners or queue for connectivity restoration when a plain retry would succeed. Swift is the only executor reporting offline for a server-side abort: reqwest maps the equivalent io `UnexpectedEof` to `HttpError { "The server terminated the connection unexpectedly" }` and never constructs `DeviceIsOfflineError`; Kotlin only claims offline after `NetworkAvailabilityProvider` confirms the network is down.

**Fix:** keep `.notConnectedToInternet` as `DeviceIsOfflineError`. For `.networkConnectionLost`, either (a) emit `HttpError` matching reqwest, or (b) — the faithful fix, since -1005 also fires on genuine mid-request connectivity drops — gate on a connectivity signal (`NWPathMonitor`, mirroring Kotlin's provider) and emit `DeviceIsOfflineError` only when the path is actually unsatisfied.

**Caveat:** `.networkConnectionLost` is listed as a Swift offline signal in the new `is_device_offline` rustdoc, so the contract text and the variant-coverage tests from 8aa3cf20 must move with the fix. The `waitsForConnectivity` caveat from Automattic/wordpress-rs#1491 doesn't help here — -1005 is reported for established connections.

Start in native/swift/Sources/wordpress-api/SafeRequestExecutor.swift at the .networkConnectionLost handling, then inspect the is_device_offline rustdoc and variant-coverage tests from 8aa3cf20. Compare the reqwest and Kotlin executor behavior and determine the appropriate connectivity signal. Done means server-side aborts no longer report offline while genuine offline cases retain DeviceIsOfflineError and the contract and tests are updated.

Written by the indexing model from the issue text.