initial: zero-trust markdown tutorials site

Single-binary Go service that renders markdown pages from a runtime
volume mount. Targeted at public, no-auth, no-WAF deployment behind a
TLS ingress; security posture is defense-in-depth at every layer:

- goldmark with no WithUnsafe — raw HTML in author markdown is stripped
- CSP without 'unsafe-inline', plus HSTS, COOP, CORP, Permissions-Policy
- static handler rejects non-GET/HEAD, directory listings, dotfiles, traversal
- content loader rejects symlinks that escape the content root, dotfiles,
  and .md files larger than 1 MiB
- per-page template trees (cloned from layout) so define-blocks don't
  collide between home/category/page
- SIGHUP triggers atomic library swap — live edits on volume, no rebuild

Locale layout content/<locale>/<category>/<slug>.md. Categories without
_index.md still appear on the home page with a humanized name. Search is
a ~70-line vanilla JS scan over /search.json?lang=<locale>; swap for a
real indexer if the corpus ever balloons.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Makefile

@@ -0,0 +1,19 @@
+.PHONY: build run dev test vet docker
+
+build:
+	go build -o automc-tutorials ./cmd/automc-tutorials
+
+run: build
+	./automc-tutorials
+
+dev:
+	go run ./cmd/automc-tutorials
+
+test:
+	go test ./...
+
+vet:
+	go vet ./...
+
+docker:
+	docker build -t git.timemachine.center/timemachine/automc-tutorials:latest .