Upgrade to Go 1.27.1 and address the lint findings it surfaces

[masih]

Go 1.25.6 is behind the toolchain the rest of the stack targets, and golangci-lint v2.8.0 does not run on Go 1.27. This moves the module, the Dockerfiles, and every workflow to Go 1.27.1 and golangci-lint v2.13.2, and fixes what the new linters report. The Go version is read from go.mod everywhere it is needed (a small scripts/go-toolchain.sh handles the patch-less go 1.28 shape), the frozen precompiles/*/legacy and utils/helpers/legacy trees are excluded from lint in .golangci.yml rather than edited, and precompiles/p256/verifier.go is left byte-identical so bump_version does not mint a new legacy copy.

Two changes go beyond lint. Go 1.27's compress/flate emits different bytes than Go 1.26 for the same input, which reaches state-sync snapshots through both the multistore zlib stream and the gzipped wasm code the wasm extension writes into it, so the multistore snapshot format is bumped from 1 to 2. Upgraded nodes restore both formats, but an old binary answers REJECT_FORMAT to every snapshot an upgraded node serves, so operators should keep old-binary snapshot providers up until the rollout completes. Separately, CommitSig.FromProto now rejects a block_id_flag outside ABSENT, COMMIT, NIL at decode instead of truncating it through uint8; a value such as 257 used to wrap to Absent and pass ValidateBasic. Both are recorded in CHANGELOG.md.

Smaller behavioural effects worth knowing about: the p2p mux now returns an error instead of silently truncating a frame header longer than 255 bytes, the Tendermint HTTP client dials with the request context so cancellation aborts a pending dial, and the EVM JSON-RPC error strings for malformed eth_call arguments changed wording because Go 1.27 implements encoding/json v1 as a shim over v2 (they still match geth, and the rpc integration tests were loosened accordingly, as were the exact-bytes gzip and JSON-error-text unit tests). The v2 shim promises identical marshal/unmarshal semantics; amino-JSON sign bytes and wasmvm Env/Info serialization were checked and the Determinism and geth-parity jobs pass. Releases up to release/v6.7 cannot be built with a Go 1.27 toolchain because of their pinned cockroachdb/swiss, so the upgrade-test harness pins each worktree's toolchain from its own go.mod and operators building old tags need to do the same.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 10, 2026, 3:31 PM

[codecov]

Codecov Report

❌ Patch coverage is 59.81308% with 86 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.12%. Comparing base (fcbbc9e) to head (52cf7c8).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-cosmos/x/auth/client/testutil/helpers.go	0.00%	19 Missing ⚠️
giga/deps/xevm/types/gov.go	12.50%	14 Missing ⚠️
x/evm/types/gov.go	12.50%	14 Missing ⚠️
sei-cosmos/client/rpc/validators.go	0.00%	4 Missing ⚠️
sei-cosmos/x/params/types/proposal/proposal.go	0.00%	4 Missing ⚠️
sei-tendermint/internal/rpc/core/mempool.go	0.00%	4 Missing ⚠️
sei-cosmos/x/distribution/types/proposal.go	0.00%	2 Missing ⚠️
sei-cosmos/x/gov/types/vote.go	0.00%	2 Missing ⚠️
sei-tendermint/cmd/tendermint/commands/debug/io.go	0.00%	2 Missing ⚠️
sei-tendermint/rpc/jsonrpc/server/http_server.go	33.33%	2 Missing ⚠️
... and 18 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4098      +/-   ##
==========================================
+ Coverage   61.36%   62.12%   +0.76%     
==========================================
  Files        2191     2105      -86     
  Lines      192106   182253    -9853     
==========================================
- Hits       117887   113233    -4654     
+ Misses      62737    61742     -995     
+ Partials    11482     7278    -4204     

Flag	Coverage Δ
sei-chain-pr	72.34% <59.81%> (?)
sei-db	74.50% <ø> (+4.48%)	⬆️
sei-db-state-db	?
sei-db-state-db-pr	83.88% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cmd/autobahn-e2e/aws.go	66.56% <100.00%> (+13.55%)	⬆️
cmd/frozen-rpc-router/router.go	77.67% <100.00%> (+12.27%)	⬆️
config/registry/registry.go	99.22% <100.00%> (+0.77%)	⬆️
config/registry/resolve.go	96.75% <100.00%> (+1.38%)	⬆️
evmrpc/block.go	87.50% <ø> (+8.22%)	⬆️
evmrpc/info.go	86.57% <100.00%> (+9.88%)	⬆️
evmrpc/server.go	89.86% <100.00%> (+4.14%)	⬆️
evmrpc/tests/mock_client.go	53.89% <100.00%> (+4.54%)	⬆️
evmrpc/utils.go	81.10% <100.00%> (+8.29%)	⬆️
giga/deps/xevm/types/ethtx/access_list.go	100.00% <100.00%> (ø)
... and 70 more

... and 527 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.