docs: bring CURRENT_STATE up to date with 0.4.3 and the scenario corpus work

[sepehr-safari]

CURRENT_STATE.md has drifted again since #136. Two mechanisms put it there and
neither involves a normal feature PR, which is where the living document is
usually kept current.

• The release PR is created by the changesets action and never touches this
  file, so 0.4.3 shipped without a record.
• Issue-only work leaves no PR at all, so Add a new scenario: heartbeat-timeout #137, Add a new scenario: firmware-update-failure #138, Add a new scenario: repeated-boot-notification #139, docs: require a scenario for every detection rule #140 and feat(core): detect a stuck meter register during an active transaction #144 exist
  with nothing here pointing at them.

Stale or missing

• Current Version says 0.4.2. 0.4.3 published 2026-07-28.
• Package Status Table says @ocpp-debugkit/toolkit is at 0.3.1. It is at
  0.4.3, so this one has been wrong since the v0.4.0 release.
• v0.4.x Releases has no 0.4.3 entry and does not list the v0.4.3 tag.
• Nothing records the first external good-first-issue contribution completing
  (feat(scenarios): add firmware update success scenario #133 for Add a new scenario: firmware-update-success #104), the changeset sizing decision (chore: scenario additions should be patch changesets, not minor #142, PR chore: size scenario changesets as patch, not minor #143), the three new
  scenario issues, the per-rule scenario invariant (docs: require a scenario for every detection rule #140), or the stuck meter
  register proposal (feat(core): detect a stuck meter register during an active transaction #144).
• Known Blockers / Decisions Pending says "None currently. All design
  decisions resolved in ADRs." feat(core): detect a stuck meter register during an active transaction #144 carries four open design questions.

Fix

Bring all of the above current, and add a section covering the scenario corpus
push and the contributor pipeline it feeds.

Documentation only. No changeset: CURRENT_STATE.md is not in the package
files list, so it does not ship to npm.