Relocate SCML ladder build tooling to scripts/ladder; keep configs/ config-only

- configs/ablations/ladder/ now holds only CC-style configs (make_scml.yaml) + README
  note, matching the existing 3 ladders. Bot ports removed from the monorepo — the
  human/* branches on CodeClash-ai/SCML are the source of truth (as with other arenas).
- Move build scaffolding (porting guide, validators, smoke/push scripts, AWS runbook,
  example agents) to scripts/ladder/ as operational tooling; add README + .gitignore
  (ports/ and out/ are regenerated, not committed).
- Fold sourcing/status from the deleted scml_sources.md into the ladder README note.

Author: john-b-yang

configs/ablations/ladder/README.md

@@ -14,15 +14,19 @@ We've typically found that googling for online leaderboards or awesome-<arena> r
 
 ### SCML OneShot (newly added)
 
-The [CC:SCML](https://github.com/CodeClash-ai/SCML) repo hosts 51 human bots on `human/*` branches:
-3 built-in `scml` baselines (greedy/random/nice) plus 48 ANAC competition agents ported from
-[`yasserfarouk/scml-agents`](https://github.com/yasserfarouk/scml-agents) (years 2021–2024). Each
-was re-expressed from its `OneShotAgent`/`OneShotSyncAgent` source into the arena's single-file
-`decide(observation)` contract (see `scml_pilot/PORTING_GUIDE.md` and `scml_sources.md`). Candidate
-sourcing, the porting recipe, and the validation/push tooling live in `scml_pilot/`. Note: unlike
-the earlier arenas, SCML's `git`-workspace had to be wired for the ladder — the `CodeClash-ai/SCML`
-repo was created (seeded with the runtime) and `SCML.Dockerfile` now `git clone`s it so `branch_init`
-works.
+The [CC:SCML](https://github.com/CodeClash-ai/SCML) repo hosts 51 human bots on `human/*` branches
+(like the other arenas, bot code lives only on the branches, not in this repo): 3 built-in `scml`
+baselines (greedy/random/nice) plus 48 ANAC competition agents from
+[`yasserfarouk/scml-agents`](https://github.com/yasserfarouk/scml-agents) (2021–2024), each
+re-expressed from its `OneShotAgent`/`OneShotSyncAgent` source into the arena's single-file
+`decide(observation)` contract. RL/learned agents were ported as heuristic-core best-effort;
+`scml2023/team_139` is deferred. Note: unlike the earlier arenas, SCML's `git`-workspace had to be
+wired for the ladder first — the `CodeClash-ai/SCML` repo was created (seeded with the runtime) and
+`SCML.Dockerfile` now `git clone`s it so `branch_init` works.
+
+The build tooling (porting guide, validators, smoke/push scripts, and the AWS run
+instructions in `RUN_ON_AWS.md`) lives in `scripts/ladder/` — it's operational one-off tooling for
+constructing porting-based ladders, reusable for future arenas.
 
 ## Config layout