build: replace ad-hoc run with a full make workflow + helper scripts

The old Makefile was a single 'run' target (hugo server + pagefind --serve).
Replace it with documented targets:

  build         hugo --gc -> public/
  index         build + pagefind --site public -> public/pagefind/
  serve / run   index + pagefind's own server on 127.0.0.1:1414 (local)
  serve-lan     static-serve public/ on 0.0.0.0:8090 for other machines
  link-check    offline internal-link scan (lychee --scheme file) -> JSON
  link-fix      comment out confirmed-dead internal links, then rebuild
  external-check network scan of external links (report-only)
  clean / all

Add scripts/:
  serve_lan.py            stdlib static server rooted at public/ (prints LAN IP)
  fix_dead_links.py       idempotent internal dead-link comment-out
  check_external_links.py external link report (drives the daily cron job)

.gitignore: add linkcheck/, resources/_gen/ (regenerable Hugo asset cache),
__pycache__/, and .hermes/.

Makefile

@@ -1,3 +1,52 @@
-run:
-	hugo server &
-	npx -y pagefind --site public --serve
+HUGO     := hugo
+PAGEFIND := npx -y pagefind
+LYCHEE   := lychee
+OUT      := public
+
+.PHONY: all build index serve run link-check link-fix external-check serve-lan clean
+
+all: index
+
+# Build Hugo content -> public/
+build:
+	$(HUGO) --gc
+
+# (Re)build the Pagefind search index from public/ -> public/pagefind/
+index: build
+	$(PAGEFIND) --site $(OUT)
+
+# Build content + index, then serve the built site WITH search on :1414 (dev preview).
+# Uses pagefind's own server. Local only (binds 127.0.0.1) -- for LAN use `make serve-lan`.
+serve: index
+	$(PAGEFIND) --site $(OUT) --serve
+
+run: serve
+
+# DEAD LINKS -- internal (offline, fast): scan the SOURCE markdown; internal links
+# resolve to file:// under public/. External links are skipped by --scheme file.
+# Output: linkcheck/internal.json (exit != 0 when dead links exist; that is fine).
+link-check: build
+	mkdir -p linkcheck
+	$(LYCHEE) --root-dir $(OUT) --default-extension html --scheme file \
+	  --format json --timeout 10 \
+	  $(wildcard content/*.md) $(wildcard content/*/*.md) > linkcheck/internal.json
+
+# Comment out confirmed dead INTERNAL page links, then rebuild content + index so they
+# leave the live page AND the search index. (External failures -> manual_review.txt.)
+link-fix:
+	python3 scripts/fix_dead_links.py --report linkcheck/internal.json --apply
+	$(HUGO) --gc
+	$(PAGEFIND) --site $(OUT)
+
+# DEAD LINKS -- external (network): scan all http/https links in content. Report-only.
+# Always exits 0; the report is the point.
+external-check:
+	python3 scripts/check_external_links.py
+
+# Serve the BUILT site on all interfaces so another LAN machine can open it:
+#   http://<this-machine-LAN-IP>:8090/    (IP printed at startup; also `hostname -I | head -1`)
+serve-lan:
+	python3 scripts/serve_lan.py
+
+clean:
+	rm -rf $(OUT) linkcheck