FS-117: consistent AutoCAD R12 DXF export

[michaelfutol]

Summary

• make the DXF envelope internally consistent AutoCAD R12 ASCII (AC1009)
• add mandatory R12 linetypes, layer 0, txt.shx, CRLF output, and corrected CENTER2 pattern
• add strict ezdxf parse/audit/round-trip validation and an AutoCAD 2025 Core Engine gate
• publish FS-117 build and release provenance

Local acceptance evidence

• node v3/tools/check-fs.js --no-browser: pass
• node v3/tools/check-fs.js: pass, 1,603 entities retained exactly after parser round trip
• current Olango project smoke: pass as GF/2F/RF, 48 columns, 103 beams, 62 slabs
• Olango DXF: 4,980 entities, 21 layers, zero parser audit errors/fixes, exact round-trip retention
• line endings: 84,398 CRLF, zero bare LF
• AutoCAD 2025 Core Engine: open/regenerate pass, no recovery message
• AutoCAD full-package render and high-resolution plan/table review: all 7 plans and all schedule/BOQ blocks present and separated

Scope exclusions

• no Protected Project Revisions
• no helper/history scripts
• no solver changes
• no broad UI or modeling changes

Rollback

Production baseline before this PR: 456633c90bf3fe49d93842501a776bdc5fd9ea61.

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Project	Deployment	Actions	Updated (UTC)
futolstructure	Ready	Preview, Comment	Jul 14, 2026 5:28am