Initial commit: Conflict Checker

Cross-discipline design-contradiction checker for construction drawing
sets. Standalone tool broken out from Iron_Bid; a pipeline stage may
later fold back into Iron_Bid.

Pipeline: PDF->images -> per-sheet assertion extraction -> deterministic
clustering by location -> per-cluster reasoning -> report.
Includes CLI (cli/run_check.py) and web UI (backend/main.py).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/code_corpus/README.md

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+# Code / standard reference corpus (Stage 7)
+
+Drop plain-text `.txt` files here. Stage 7 (`code_review.py`) retrieves the most
+relevant excerpts and lets the model cite section numbers **only** when they
+appear in a retrieved excerpt. An empty corpus is valid — Stage 7 then runs
+reasoning-only and cites nothing.
+
+## File naming → standard
+
+The standard is inferred from the filename prefix:
+
+| prefix          | standard |
+|-----------------|----------|
+| `ada*.txt`      | ADA      |
+| `tas*.txt`      | TAS      |
+| `ibc*.txt`      | IBC      |
+| `ifc*.txt`      | IFC      |
+| `iebc*.txt`     | IEBC     |
+| `energy*.txt`   | ENERGY   |
+
+(Only `.txt` files are loaded; this `README.md` is ignored.)
+
+## Format
+
+Plain text, chunks separated by a blank line. If a chunk begins with a section
+number (e.g. `404.2.3 Doors ...`), that number is captured as its section id and
+is what the model may cite.
+
+```
+404.2.3 Door and Gate Opening Force
+Fire doors shall have a minimum opening force allowable by the appropriate
+administrative authority. The force for pushing or pulling open ...
+
+405.2 Slope
+Ramp runs shall have a running slope not steeper than 1:12.
+```
+
+## Licensing note
+
+- **ADA 2010 Standards** and **Texas Accessibility Standards (TAS)** are
+  government documents and can be included here.
+- **IBC / IFC / IECC** are ICC copyrighted works — do **not** paste their text
+  unless you have a license. Provide your own licensed copy if needed.