Checkpoint experiments through SWE pilot v2

docs/migration/README.md

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+# September 8 repository consolidation
+
+`messageboardbench` is now the sole working repository for this experiment.
+The old `messageboard` directory was retired to
+`../../../archive/messageboard-20260908`; its remaining files and Git history
+were preserved, including personal notes, old paper drafts and obsolete code.
+Its credentials and environment were not imported into this repository.
+
+Selected moves:
+
+| Original path under messageboard | New path under messageboardbench |
+|---|---|
+| `scratchpad/board-interface-v2-sept8` | `results/board-interface-v2-sept8` |
+| `scratchpad/board-pilot-sept8` | `results/board-pilot-sept8` |
+| `scratchpad/model-comparison-sept7` | `results/model-comparison-sept7` |
+| `scratchpad/team-pilot-sept7` | `results/team-pilot-sept7` |
+| `scratchpad/token-comparison-sept7` | `results/token-comparison-sept7` |
+| `scratchpad/sept10-revision` | `results/sept10-revision` |
+| `research/09-shared-scratch-design.md` | `docs/research/09-shared-scratch-design.md` |
+| `research/10-private-scratch-public-board.md` | `docs/research/10-private-scratch-public-board.md` |
+| `research/sources/team-scratch` | `docs/research/sources/team-scratch` |
+| `research/sources/board-design-sept7` | `docs/research/sources/board-design-sept7` |
+
+[The manifest](messageboard-20260908.json) lists all 491 retained files, their original
+and destination paths, byte counts and SHA-256 hashes. All were verified after
+moving. Frozen evidence was not rewritten to hide the move. Given an old absolute
+path, strip the manifest's `source_root` and look up `old_path`; `path` is relative
+to this repo. Unselected paths map into the retired archive instead.
+
+The current README, workflow docs, EXPERIMENT and AGENTS files supersede historical
+plans. The existing upstream `../impossiblebench` dependency remains required;
+retiring the research repo does not replace that dependency.
+
+Run `just evidence-check` to verify all migrated bytes. Recompute analyses using
+the portable scripts in `scripts/analysis/`, writing into fresh directories rather
+than replacing frozen results.