v12.0.0 — pin hygiene + docs (opt-in major)

Why v12 (not moving v11)

v11 stays frozen so existing consumers (including Kunobi on @v11) do not silently pick up action major bumps.

v12 / v12.0.0 is the opt-in line for:

Change	PR
Docs: drop Node 18; document pin policy	#121
actions/checkout @v7 (direct pins)	#122
upload-artifact @v7, download-artifact @v8	#122
Dependabot for github-actions	#122

Migrate a consumer (e.g. kunobi-frontend)

# before
uses: zondax/_workflows/.github/workflows/_checks-ts.yaml@v11

# after
uses: zondax/_workflows/.github/workflows/_checks-ts.yaml@v12
# or pin: @v12.0.0

Smoke one PR, then roll the rest of the call sites.

Rollback

Keep or revert to @v11 (unchanged content).

Follow-ups

• #119 one node/pm bootstrap story
• #120 align ubuntu-ci 22.04 vs 24.04
• #123 pilot process before future floating moves