Publish CLAUDE.md snapshot at /CLAUDE.md, linked from footers

Serve it as text/plain on deploy so browsers display the raw text
instead of downloading; add .dockerignore so local image builds can't
ship stale _site or host node_modules.

Makefile

@@ -9,13 +9,15 @@ build:
 dev:
 	docker run --rm -v $$(pwd):/app -w /app -p 8080:8080 node:22-alpine sh -c "yarn install && yarn dev --port 8080"
 
+# CLAUDE.md is re-uploaded as text/plain: sync guesses text/markdown for .md,
+# which Firefox downloads instead of displaying in the tab.
 deploy: build
 	docker run --rm \
 		-e AWS_ACCESS_KEY_ID \
 		-e AWS_SECRET_ACCESS_KEY \
 		-e AWS_DEFAULT_REGION \
 		unprompted \
-		aws s3 sync /site $(S3_BUCKET) --delete
+		sh -c "aws s3 sync /site $(S3_BUCKET) --delete && aws s3 cp /site/CLAUDE.md $(S3_BUCKET)/CLAUDE.md --content-type 'text/plain; charset=utf-8'"
 
 invalidate:
 ifdef CF_DISTRIBUTION_ID