chore(tooling): retire atlas geometry generator + LLM naming cluster (D-223 #951)

The procedural server cascade (Phase 4) and the frozen names-only pool
supersede the Python atlas geometry generator and the LLM namer. Retire:

- generate_atlas.py (geometry production — cities/roads/rivers placement)
- gemma_naming.py, naming_core.py + tests (test_batch_naming,
  test_register_selection, qa_naming) and run-atlas-naming.sh (the LLM
  place-namer; its output is now the frozen pool)
- apply_name_fixes.py (name-field patches), fix_fewshot_bleed.py /
  prune_atlas_features.py (geometry tools)
- import_city_names.py (redundant with import_economics name-pool path)

Pipeline updates: drop the generate_atlas step + atlas-generate /
test-atlas-determinism targets from the Makefile; remove generate_atlas
from the stamp registry (import_economics is the sole regen-db generator);
drop run-atlas-determinism from tests/run-all; refresh stale references in
schema_version, backfill_cultural_corridor, earth_blocklist (kept as
reference data), populate_terrain_reference, and heightmap.rs.

The Gemma prompting methodology is preserved in
docs/gemma-naming-methodology.md (separate commit).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tooling/schema_version.py

@@ -8,7 +8,6 @@ require a bump.
 
 Imported by:
   tooling/economy-db/import_economics.py
-  tooling/planet-gen/generate_atlas.py
 """
 
 SCHEMA_VERSION = "1.0.0"