feat(build): split makefile, ensure tools isolation.

[Zenithar]

[Build] Modularise Makefile and isolate tool management

Summary

What: Splits the monolithic 530+ line Makefile into focused modules under mk/ and introduces stamp-based isolated tool management in .tools/.

Why: The original Makefile was difficult to navigate, mixed concerns (build, test, lint, deploy, tool installation), and installed tools globally into $GOBIN, causing version conflicts between projects and non-reproducible developer environments.

How: The root Makefile becomes a thin entry point that sets shared variables and includes seven domain-specific modules. All tool binaries are now installed in a project-local .tools/bin/ directory, with stamp files that track versions, so Make skips reinstalling when versions haven't changed.

Changes

Build System (Makefile, mk/*.mk):

• Refactored monolithic Makefile (530 lines) into a thin entry point (~100 lines) with shared variables
• Created mk/tools.mk — Stamp-based tool version management, all tools install to .tools/bin/
• Created mk/docker.mk — Docker build, save, and push targets for injector/handler/manager
• Created mk/test.mk — Unit tests, e2e tests, and chaosli test targets
• Created mk/generate.mk — CRD manifests, deepcopy, protobuf (DRY template), and mock generation
• Created mk/lint.mk — fmt, vet, lint, and spellcheck targets
• Created mk/lima.mk — Lima cluster lifecycle, deployment, and local development helpers
• Created mk/ci.mk — CI-specific targets (minikube, headers, licenses, deps, release, Datadog agent)
• Added make help target that auto-generates help from ## comments

Tool Isolation:

• All tools install to .tools/bin/ instead of global $GOBIN
• Stamp files in .tools/stamps/ track installed versions — version bumps trigger reinstall, same version is a no-op
• Added .tools/ to .gitignore
• PATH is extended at the Makefile level to include .tools/bin/
• clean-tools target to wipe the local tool directory

Protobuf:

• Regenerated chaosdogfood.pb.go and disruptionlistener.pb.go with protoc-gen-go v1.36.11 (aligned with go.mod)
• Protobuf generation now uses a DRY foreach template instead of duplicated targets
• protoc-gen-go and protoc-gen-go-grpc are managed as isolated tools with pinned versions

Other:

• Replaced = (recursive) with := (simple) for most variable assignments where appropriate
• Standardised .PHONY declarations across all targets
• Aligned variable formatting for readability

Testing

Unit Tests:

• make test still works as before (generates + runs ginkgo suite)
• make lint installs golangci-lint locally and runs

Manual Testing:

• make help displays all available targets
• Tools install to .tools/bin/ on first use
• Subsequent make invocations skip tool install (stamp hit)
• make clean-tools removes .tools/
• make generate works with locally installed controller-gen
• make manifests works with locally installed controller-gen + yamlfmt

Breaking Changes

Potential behavioural change:

• Tools are no longer installed into global $GOBIN / $GOPATH/bin. They now go to .tools/bin/. This is intentional but means running golangci-lint or controller-gen directly outside of Make will use the system-installed version, not the project-pinned one.
• The spellcheck-report and spellcheck-format-spelling targets were removed (they were rarely used utilities).

Dependencies

• No new Go dependencies added
• protoc-gen-go bumped from v1.27.1 to v1.36.11 (aligned with go.mod dependency and generated code updated accordingly)
• No changes to go.mod / go.sum

Checklist

• All existing Make targets preserved (no functional regression)
• .tools/ added to .gitignore
• Generated protobuf code regenerated with updated tooling
• make help provides discoverability for all targets
• No sensitive information in committed files

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 39.29% (+0.00%)

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[Zenithar]

Closing this PR in favour of a deeper building system restructuring.