Release v28.0.0

[Shaptic]

Release PR for horizon v28.0.0 — part of the Protocol 28 GA release train (stellar/go-stellar-sdk#5967).

Carries the three review findings from #213, deliberately landed here instead of on the merge PR to avoid re-running the ~1h integration suite:

1. horizon-release.yml — the deprecation egrep ran before actions/checkout, scanning an empty workspace, so the negated exit always succeeded and the gate could never fail a release. Checkout moved ahead of it (and bumped to @v4).
2. release-readiness.yml — the empty-pin gate still matched the pre-Decompose Horizon integration tests into a callable workflow #202 PROTOCOL_<N>_STELLAR_RPC_DOCKER_IMG env-var shape, so it never inspected the lowercase stellar_rpc_docker_img inputs horizon.yml actually defines; an empty pin took the success path even when targeting main. Now matches the real key in both quote styles — verified silent on the current file, and firing on '', "", bare, and whitespace-only values while still ignoring the commented-out leg.
3. CHANGELOG.md — the 28.0.0 entry claimed MaxSupportedProtocolVersion needed no bump; true only relative to protocol-next, since released 27.0.0 shipped 27.

Once this merges, its merge commit on main is the tag target for v28.0.0 (convention: tags must be main-reachable).

Note: CI legs still pin stellar/unsafe-stellar-core:28.0.0-3486.2332980a1.jammy. The swap to stellar/stellar-core is a separate pre-tag step, still blocked on that image publishing.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Prepares Horizon v28.0.0 by correcting release safeguards and release documentation.

Changes:

• Runs deprecation checks after repository checkout.
• Validates actual stellar_rpc_docker_img workflow inputs.
• Corrects the Protocol 28 changelog entry.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
CHANGELOG.md	Documents the protocol-version bump.
.github/workflows/release-readiness.yml	Fixes empty RPC image-pin detection.
.github/workflows/horizon-release.yml	Checks out source before deprecation scanning.

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[Shaptic]

Added 644f6fc2: raises the unit-test timeout to -timeout 45m per package.

The test (ubuntu-24.04, 1.25, 16) failure was two packages hitting Go's 10m per-package default (the step passed no -timeout at all, unlike the integration suite's explicit -timeout 75m):

• internal/ingest — TestCoreLCMIngestion ran the full 10m and was still producing sub-tests when killed. It walks ~856 LedgerCloseMeta fixtures (691 under InvokeHostFunctionTests); sub-tests are t.Parallel(), but each provisions its own Postgres database and runs the whole migration suite.
• internal/db2/history — cumulative package time exceeded 10m; the test running at the deadline (TestStreamAllOffersRequiresTx) was only 5s in.

Neither is a hang — both were making progress — so this is a genuine budget problem, and the fixture corpus grows every protocol. Filed as a follow-up on the train issue: the durable fix is to stop re-migrating a fresh database per fixture in TestCoreLCMIngestion, which would cut the bulk of that runtime.