Consolidate dependency upgrades to latest; drop scodec; fix versionPolicyCheck

[jchapuis]

Summary

Replaces the 21 open Scala Steward dependency PRs with a single consolidated update to the latest stable versions across the build, and removes the endless-scodec-helpers module.

Why all the Steward PRs were failing

Every Steward PR failed CI — but not because of the bumps. The CI command reaches versionPolicyCheck (which runs after compile/+test), and that step couldn't resolve io.github.endless4s:endless-scodec-helpers_3:0.31.1 from Maven Central:

Error downloading io.github.endless4s:endless-scodec-helpers_3:0.31.1
  not found: …/endless-scodec-helpers_3-0.31.1.pom

The scodec module was switched to Scala-3-only, but the _3 artifact was never published (only the stale _2.13 exists; every other module is published at 0.31.1). This pre-existing infra blocker sank every PR regardless of content. Since the _3 artifact never shipped, there is no Scala-3 consumer to break — so the module is dropped, clearing the blocker.

Upgrades (latest stable)

akka is intentionally pinned at 2.6.20 — the last Apache-2.0 release before the BSL license change.

Area	Version
Scala	2.13.18 / 3.8.4
sbt	1.12.11
pekko	1.6.0
cats-effect	3.7.0
http4s	0.23.34
circe	0.14.15
logback	1.5.34
log4cats	2.8.0
munit / munit-scalacheck / munit-cats-effect	1.3.2 / 1.3.0 / 2.2.0
scalacheck-effect	2.1.0
kind-projector	0.13.4
wartremover	3.5.8
scoverage	2.4.4
sbt-ci-release	1.11.2
sbt-scalafmt / scalafmt	2.6.1 / 3.9.10
scalapb compilerplugin	0.11.20

Other change

-Xfatal-warnings → -Werror. Scala 3.8 deprecated the -Xfatal-warnings alias; because the flag turns all warnings into errors, its own deprecation warning became a build error. -Werror is valid on both 2.13 and 3.x.

Validation (local, mirrors CI)

• ✅ scalafmtCheckAll
• ✅ Cross-compile all modules on 2.13.18 and 3.8.4 (no warnings/warts)
• ✅ Tests pass: 173 on 2.13.18 (core 98, circe 1, pekko-rt 2, akka-rt 2, example 70 incl. PekkoExampleAppSuite/AkkaExampleAppSuite integration), plus runtimes+example 74 on 3.8.4
• ✅ versionPolicyCheck passes for all 5 published modules (the original blocker)
• ✅ documentation/makeSite builds (scodec scaladoc reference removed)

Supersedes

Closes the Steward PRs: #439, #462, #463, #471, #477, #478, #479, #484, #486, #488, #492, #495, #505, #506, #507, #508, #510, #512, #513, #516, #517

🤖 Generated with Claude Code

[what-the-diff]

PR Summary

• Upgraded Development Tool Versions

  • Upgraded the version of Scalafmt, a tool for formatting code. This brings some improvements and bug fixes available in the new version.
  • Updated Scala versions in the build configuration. This keeps the codebase up to date with the latest Scala features and improvements.
  • Updated the 'kind-projector' compiler plugin. This plugin helps with type-inference in Scala, so our code remains easy to read and write.

• Compiler Adjustments

  • Modified compiler options for better error handling during the build process. This enhancement ensures code errors are treated seriously and addressed promptly during development.

• Removed Scodec Helper Support

  • Removed support for scodecHelpers from the project. By doing so, the project is streamlined and won't aggregate this helper anymore.

• Improved Documentation

  • Updated textual and technical references related to the removed endless-scodec-helpers. This makes the documentation clean and current.

• Boosted Dependency Versions

  • Updated various dependencies to their latest versions. This ensures the project benefits from the latest improvements, security fixes and feature enhancements offered by these third-party libraries.

• Build Properties Update

  • Updated the SBT version used in build properties. This might bring improvements in build speed and stability.

• Plugin Upgrades

  • Upgraded different plugins like Wartremover, Scoverage, sbt-ci-release, and sbt-scalafmt. Upgrading plugins usually brings new features and bug fixes that can improve the development experience.

• Pruned Redundant Code

  • Removed redundant Scodec-related files and tests. This keeps the codebase lean, manageable, and focused on the current needs.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.05%. Comparing base (dec3c01) to head (4c299f4).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #518   +/-   ##
=======================================
  Coverage   89.05%   89.05%           
=======================================
  Files          73       73           
  Lines         877      877           
  Branches      116      115    -1     
=======================================
  Hits          781      781           
  Misses         96       96           

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