fix(mapgen-studio): odd-Q flat-top orientation, canonical hex-space lattice, and tile-mesh contract

[mateicanavra]

Fixes tile.hexOddQ layers rendering with the wrong hex orientation and establishes a consistent tile-mesh visual contract.

Hex orientation fix

tile.hexOddQ was incorrectly rendered using pointy-top geometry — the same path as tile.hexOddR — producing rotated tiles on a sheared lattice. Column-offset (odd-Q) layouts are flat-top by construction. The fix aligns odd-Q rendering with mapgen-core's canonical hex space (projectOddqToHexSpace): columns √3·size apart, rows 1.5·size apart, odd columns shifted down 0.75·size. This is the same coordinate frame the Delaunay mesh and all world.xy layers are built in, so tile layers now co-register correctly with mesh and world stages.

A new hexPolygonOddQ function produces the flat-top hexagon that exactly tiles this lattice (vertical pitch compressed to the 1.5·size row spacing, no gaps or overlaps). The grid geometry builder dispatches to hexPolygonOddQ or hexPolygonPointy based on space. The boundsForTileGrid odd-Q branch is corrected to cover the same lattice. The intermediate pointy-top axial conversion helpers that were previously used for both spaces are removed.

Tile-mesh contract

• UNKNOWN_COLOR (noData and non-finite values) is now fully transparent, so unfilled tiles draw nothing and leave no phantom mesh over the canvas background.
• Hex stroke alpha follows the tile's fill alpha — transparent tiles also drop their borders.
• The hardcoded near-black border literal is replaced with an exported TILE_BORDER_COLOR, a mid-luminance slate that remains legible against white, black, and graphite canvas backgrounds.

Tests added

• Per-space vertex orientation assertions confirming odd-R is pointy-top and odd-Q is flat-top.
• Canonical lattice spacing verification for odd-Q (column pitch, row pitch, odd-column offset).
• noData tile invisibility: zero fill alpha and zero stroke alpha, with a filled neighbor retaining its border.

[github-actions]

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[mateicanavra]

Merge activity

• Jun 12, 8:50 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jun 12, 9:59 PM UTC: Graphite rebased this pull request as part of a merge.
• Jun 12, 9:59 PM UTC: @mateicanavra merged this pull request with Graphite.