Episode: Assembled globe export

EPISODE-GOAL

Record each tile’s placement in manifest.json at build time and add an assemble mode that merges the tile STLs into one positioned mesh, so the assembled globe can be imported into any mesh viewer (OnShape, FreeCAD, MeshLab, Blender) for inspection.

EPISODE-PHASE

phase 1

EPISODE-ACCEPTANCE

• Does manifest.json record per-tile placement (center_lat, center_lon, z_bottom) for every built tile?
• Does stl_tiles_build.py assemble write globe.stl (merged binary STL), globe.obj (per-tile groups), and globe-assembly.json into dataflow.out/stl-assembled/ from an existing tile set and its manifest?
• Does the assembled mesh match the globe geometry: total triangle count equals the sum of per-tile counts, and the bounding radius stays within R + base + relief?
• Do adjacent tiles’ shared boundary vertices coincide after placement within print tolerance (1e-3 mm)?
• Is the whole change reviewable in one sitting?

EPISODE-RISKS

• Is the placement (rotation from the tile-local frame, translation by z_bottom along the local up axis) exact enough that shared boundaries coincide — the neighbors sample the same global grid, but each is placed in its own frame?
• Does the merged mesh stay intended-for-viewing only (internal coincident faces make it unsuitable for printing), and is that stated in the output and the README?

EPISODE-TASKS

• Extend run_build to record center_lat, center_lon, and z_bottom in each manifest tile entry.
• Add pure-Python placement helpers (placement from a manifest entry; world transform of a placed point) to stl_tiles_build.py.
• Add the assemble mode: read the manifest and tile STLs, apply each placement, write the merged STL/OBJ/assembly JSON into dataflow.out/stl-assembled/.
• Add assemble --check: triangle-count sum, bounding radius, and adjacent-tile shared-edge coincidence.
• Extend tests/04-stl-tiles-math.sh with placement-transform invariants and a synthetic adjacent-pair coincidence check; extend the tool-gated build test to run assemble + check on its region output.
• Add a Makefile assemble target and document the output in the README.
• Run assemble on the full 42-tile set and verify the acceptance counts.

EPISODE-OUTPUT

Report the placement math, the changed files, the assembled-output file sizes, and the --check result.

EPISODE-FILES

• scripts/stl_tiles_build.py — existing (build manifest + new assemble mode)
• scripts/stl-tiles-build.sh — existing (mode pass-through, usage comment)
• tests/04-stl-tiles-math.sh — existing
• tests/03-stl-tiles-build.sh — existing
• Makefile — existing
• README.md — existing

EPISODE-BRANCH

llm/episode-01