[starius]

Migrate Loop to the btcd v2 modules and Go 1.26.8, rebased onto the current master. Exported Bitcoin address, transaction, hash, script, and chain types now use the corresponding v2 packages. Preserve the current swap-fee, withdrawal, and minimum-runtime-lnd behavior while updating the dependency graph.

Use released lndclient v0.21.0-3, the v2-compatible lnd and Aperture revisions, and the matching wallet and chain modules. Keep Taproot Assets on the fixed v0.8.6 code with a v2 compatibility migration rather than switching to main's different API and incomplete v0.8.6 fix set.

Use lnd revision f2963ce1fd19, which contains the released v0.21.4 forwarding-response recovery and replay fixes, rather than the older v2 snapshot. Align the SQL, queue, and result-helper modules with that revision and build with Go 1.26.8.

Module checks honor the configured Go proxy to avoid Git cache fetch races, while retaining all four tidy checks and the failure on a modified working tree.

Companion migrations

• Taproot Assets #2366, targeting v0.8: preserves the release fixes, migrates the patched TLV module, and recognizes pgx v5 serialization conflicts so PostgreSQL transactions retry correctly. Loop depends on this migration.
• Pool #524: v2 types, regenerated mocks, Go 1.26.8 build tooling, and the lnd runtime floor required by L402 payments.
• Faraday #255: v2 types and matching build dependencies.
• Lightning Terminal #1438: integrates all four upgraded subservers. Loop's compatibility jobs select an immutable revision of this branch and replace Loop plus both RPC modules with the current checkout.

Temporary fork replacements pin immutable source revisions. Before release, replace these with accepted upstream revisions or tags. Review and land Taproot Assets, Pool, and Faraday first; then Loop and its RPC modules; then LiT. Tagged shared dependencies and subservers can be adopted at each stage.

Validation

• Loop: full SQLite race suite; PostgreSQL race checks for the database, Instant Out, static-address, and sweep-batcher packages; configured lint; all module checks; generated CLI/daemon docs check.
• LiT: a race-tested database restart regression for pending lnd settle/fail responses and their circuits; full unit race suite with the normal service tags, embedded UI and regtest binary builds, and all eight selected terminal integration cases.
• Taproot Assets: full unit suite, patched TLV race tests, PostgreSQL conflict regression, and repeated cache-deadline/driver-error checks.
• Pool and Faraday: unit race suites and their CI checks.

Keep this draft while the coordinated dependency migrations are reviewed and the temporary pins are replaced. The btcd v2 import changes affect Go callers; the runtime lnd minimum remains v0.19.0-beta, based on the actual RPC behavior Loop requires.

Pull Request Checklist

• Add an entry to docs/release-notes/release-notes-next.md, or apply the no-changelog label.

[hieblmi]

Taproot Assets compatibility

Please bump github.com/lightninglabs/taproot-assets to v0.8.1. This PR already handles its updated rfqmath.UnitsToMilliSatoshi signature, and the bump keeps Loop compatible with litd versions using tapd v0.8.1.

Since v0.8.1 still uses the legacy btcd packages, Loop needs the temporary btcd-v2 replacement. Go does not propagate replace directives to downstream modules, so LiT needs the same replacement until a btcd-v2-compatible Taproot Assets release is available. Please re-run the LiT compatibility jobs with that setup.