Implement mcdoc v0.1.0: public documentation server

Single-binary Go server that fetches markdown from Gitea (mc org),
renders to HTML with goldmark (GFM, chroma syntax highlighting,
heading anchors), and serves a navigable read-only documentation site.

Features:
- Boot fetch with retry, webhook refresh, 15-minute poll fallback
- In-memory cache with atomic per-repo swap
- chi router with htmx partial responses for SPA-like navigation
- HMAC-SHA256 webhook validation
- Responsive CSS, TOC generation, priority doc ordering
- $PORT env var support for MCP agent port assignment

33 tests across config, cache, render, and server packages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Makefile

@@ -0,0 +1,31 @@
+.PHONY: build test vet lint clean docker all devserver
+
+LDFLAGS := -trimpath -ldflags="-s -w -X main.version=$(shell git describe --tags --always --dirty)"
+
+mcdoc:
+	CGO_ENABLED=0 go build $(LDFLAGS) -o mcdoc ./cmd/mcdoc
+
+build:
+	go build ./...
+
+test:
+	go test ./...
+
+vet:
+	go vet ./...
+
+lint:
+	golangci-lint run ./...
+
+clean:
+	rm -f mcdoc
+
+docker:
+	docker build --build-arg VERSION=$(shell git describe --tags --always --dirty) -t mcdoc -f Dockerfile .
+
+devserver: mcdoc
+	@mkdir -p srv
+	@if [ ! -f srv/mcdoc.toml ]; then cp deploy/examples/mcdoc.toml srv/mcdoc.toml; echo "Created srv/mcdoc.toml from example — edit before running."; fi
+	./mcdoc server --config srv/mcdoc.toml
+
+all: vet lint test mcdoc