Ironwood (NU6.3) SDK + Orchard→Ironwood migration bridge

[peachbits]

Ironwood (NU6.3) v1: SDK 2.7.0-rc.2 + the Orchard sweep

Stacked on #69. Restructured 2026-07-21 to v1-only (the previous full migration-lifecycle bridge moved to the stacked v2 PR): v1 ships what the app needs for the fork with no privacy machinery, per the two-phase product decision. Retargeted to the released SDK 2.7.0-rc.2, which ships Ironwood and exposes the sweep as a single proposeOrchardToIronwoodMigration proposal — identical on iOS and Android. That replaced the earlier prototype's migration engine (schedules, note splitting, a state machine), so this PR no longer bridges any of it.

What's here

1. Pin SDK 2.7.0-rc.2 + build inputs — the first released SDK line carrying Ironwood, replacing the unreleased branch head this PR previously rode (that branch rebased out from under us twice). The Edge-hosted one-time FFI build is gone: the release ships its own libzcashlc.xcframework.zip, which update-sources downloads and verifies against the checksum the SDK's own Package.swift declares. Also carries TreeState.ironwoodTree (field 7) for checkpoint generation, and bumps zcash-android-sdk (plus the incubator) from 2.5.2 to 2.7.0-rc.2 — now on Maven Central. That SDK ships Kotlin 2.3 metadata, which the app already provides (kotlinVersion = "2.3.20"). Swift dependency versions are unchanged (grpc 1.27.3 / NIO 2.95.0 / protobuf 1.35.1 / SQLite 0.15.5), so the vendored deps binary and piratechain consumer mode are unaffected.
2. BalanceEvent: Ironwood pool fields — both platforms; the deprecated summed fields include the pool.
3. The migration surface, identical on both platforms — Synchronizer.proposeOrchardToIronwoodMigration builds the sweep (the SDK spends every Orchard note to the wallet's own address, fee chosen so no Orchard change remains, Sapling and transparent untouched, all-or-nothing), which the app broadcasts through the ordinary createTransfer pipeline. Tools.getIronwoodActivationHeight answers from consensus constants (ZIP 258) — no SDK exposes an accessor — so it works on Android today. There is deliberately no migration state to poll: whether to offer the sweep follows from activation height, sync state and the Orchard balance, and broadcasting spends those notes. Android calls the same API on its own SDK — no runtime seam, no feature flag, no opt-in source set.

Verification

• Full update-sources regen from cleared caches against upstream's FFI (RC=0); vendored checkout is exactly the tag; vendored deps rebuilt.
• The Swift bridge compiles against the real 2.7.0-rc.2, and every commit compiles the Android module against zcash-android-sdk 2.7.0-rc.2 (the first time that code has been type-checked).
• develop-worktree Release build: BUILD SUCCEEDED, 0 undefined zcash/grpc/NIO symbols with the piratechain consumer co-installed, the Orchard->Ironwood FFI linked and the old migration symbols absent; app installs, launches and runs clean.

Follow-ups

• Swap to the final 2.7.0 tag when it ships (pins-only commit). A 2.8.0-rc.1 iOS prerelease exists, but Maven's newest Android is 2.7.0-rc.2, so rc.2 is where both platforms align.
• The full guided-migration lifecycle bridge is the stacked v2 PR (held for live validation).

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Note

High Risk
Touches wallet balances, transaction reporting, and native SDK/FFI pins across iOS and Android; migration proposals affect how Orchard funds are swept at NU6.3.

Overview
Upgrades iOS and Android Zcash SDKs to 2.7.0-rc.4 for Ironwood (NU6.3): Android dependencies bump, Swift sources pin to the release commit, and update-sources pulls libzcashlc from the SDK’s own Package.swift binary target with checksum verification instead of a custom Edge FFI build.

Balance and migration API: BalanceEvent adds ironwoodAvailableZatoshi / ironwoodTotalZatoshi on both platforms; deprecated wallet totals in JS now include Ironwood. Cross-platform bridges expose Synchronizer.proposeOrchardToIronwoodMigration (Orchard sweep proposal for normal createTransfer) and Tools.getIronwoodActivationHeight (ZIP 258 consensus heights). Checkpoint tooling adds TreeState.ironwoodTree to the bundled lightwalletd proto so generated checkpoints retain Ironwood tree state after activation.

Transaction delivery fix: emitExistingTransactions plus a subscribe() call replays the full transaction set once JS listeners are attached, fixing txs that mined while the app was closed or before listeners existed and would otherwise stay pending forever. Android records emitted txs to avoid duplicate full replays from the collector.

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