Fix gen-docs CI: run protoc-gen-doc on host instead of stale container

[follesoe]

Fixes #271

Problem

The Generate documentation workflow fails on every push to master, at the Checkout source step — before any docs are generated. It runs inside container: pseudomuto/protoc-gen-doc:1.5.1, whose ~4-year-old Alpine/musl base can no longer host the Node binary GitHub injects to run JS actions (actions/checkout). With Node 20 being deprecated, the runner now injects Node 24, which needs pthread_getname_np (musl ≥ 1.2.3):

Error relocating /__e/node24_alpine/bin/node: pthread_getname_np: symbol not found

Bumping actions/checkout doesn't help — the failing binary is the runtime the runner injects, not the action's code.

Fix (Option 1 from the issue)

Drop the container and install the toolchain directly on ubuntu-latest:

• protoc via apt (protobuf-compiler)
• protoc-gen-doc via go install …@v1.5.1 (Go is preinstalled on runners)
• add $(go env GOPATH)/bin to $GITHUB_PATH so protoc finds the plugin

protoc-gen-doc is pinned to v1.5.1 — the same version as the old container — so the generated HTML is identical. The doc-generation command, triggers, secrets, and Azure upload (container: protocoldefinitions, artifact docs) are unchanged.

Also removed the leftover debug steps (Print path, List files, List doc files).

Why not the alternatives

• Buf migration (Option 2): best long-term, but a real migration (adds buf.yaml/buf.gen.yaml) — out of scope for a CI hotfix.
• Community rebuilt image (Option 3): trades one stale dependency for a less-trusted one.
• ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION stopgap: Node 20 is on a removal path; only buys time.

Validation

• Workflow YAML parses cleanly.
• Full verification is the workflow run itself (it only triggers on push to master), so it will be exercised once merged.

🤖 Generated with Claude Code