refactor(forks): rename MONAD_NEXT to MONAD_TEN, add no-op MONAD_NEXT

[pdobacz]

DRAFT, because this should be merged only after category-labs/monad actually gates MIP-8 on MONAD_TEN

🗒️ Description

Renames the MIP-8 fork MONAD_NEXT to MONAD_TEN, and adds a fresh no-op
MONAD_NEXT after it as the landing spot for the next MIPs.

Not included, deliberately:

• No MONAD_TENToMONAD_NEXTAtTime15k transition fork — no test targets it, and
  a transition across a no-op boundary asserts nothing.
• No FORK_REVISION_SCHEDULES entry in the monad runloop consumer — there is no
  monad revision for MONAD_NEXT yet. Consuming a MONAD_NEXT fixture fails
  with no monad revision schedule for network MONAD_NEXT until one exists. CI
  fills --until=MONAD_TEN, so no such fixture is produced today.

Generated JSON fixtures do not differ except fork name and source hash in metadata

Greptile Summary

This PR renames the MIP-8 fork to MONAD_TEN and introduces MONAD_NEXT as its no-op successor.

• Copies the former MONAD_NEXT specification into the new MONAD_TEN package and updates fork references and MIP-8 tests.
• Adds MONAD_TEN and MONAD_NEXT ordering, transition definitions, and consumer revision schedules.
• Restricts configured CI fixture generation to MONAD_TEN and updates documentation.

Confidence Score: 3/5

This PR should not merge until the unsupported MONAD_NEXT revision schedule and discoverable no-op transition are removed or the Monad runloop supports revision 11.

Selecting MONAD_NEXT generates and consumes fixtures that are routed to revision 11 even though MONAD_NEXT is only a behaviorally identical placeholder and no corresponding runloop revision exists.

Files Needing Attention: packages/testing/src/execution_testing/client_clis/clis/monad.py; packages/testing/src/execution_testing/forks/forks/transition.py

Important Files Changed

Filename	Overview
packages/testing/src/execution_testing/client_clis/clis/monad.py	Renames revision 10 to MONAD_TEN but prematurely maps the placeholder MONAD_NEXT and its transition to unsupported revision 11.
packages/testing/src/execution_testing/forks/forks/transition.py	Renames the MIP-8 transition and adds a discoverable no-op MONAD_TEN-to-MONAD_NEXT transition.
packages/testing/src/execution_testing/forks/forks/forks.py	Moves MIP-8 behavior to MONAD_TEN and defines MONAD_NEXT as an identical subclass.
src/ethereum/forks/monad_ten/fork.py	Adds the renamed MONAD_TEN specification implementation copied from the former MONAD_NEXT fork.
.github/configs/feature.yaml	Stops normal and runloop CI fixture generation at MONAD_TEN, avoiding placeholder MONAD_NEXT fixtures in current CI.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  N9[MONAD_NINE] -->|MIP-8 at 15k| T[MONAD_TEN / revision 10]
  T -->|exported no-op transition at 15k| N[MONAD_NEXT / configured revision 11]
  N --> C[Monad fixture consumer]
  C --> R[eest-runner receives unsupported revision 11]

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Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/testing/src/execution_testing/client_clis/clis/monad.py:39-42
**Unsupported revision 11 schedule**

When MONAD_NEXT or its exported transition is selected, these schedules send revision 11 to `eest-runner` even though MONAD_NEXT is only a no-op placeholder with no corresponding Monad revision, causing unsupported fixture execution instead of the documented `no monad revision schedule` rejection.

_{Reviews (1): Last reviewed commit: "update README fork range to MONAD_TEN" | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

[QEDK]

LGTM.