docs(releaser): release v1.5.1 — documentation site, fuzzing completeness

- Add Hugo + Geekdoc documentation site (docs/): installation, CLI
  reference, configuration, CI integration, and changelog pages; explicit
  menu bundle nav so all pages appear in the sidebar on every page
- Add Gitea CI workflow (.gitea/workflows/docs.yml): builds on push to
  main when docs/** changes, deploys minified site to gh-pages branch
- Add docs:setup / docs:serve / docs:build Taskfile tasks; theme bundle
  downloaded at build time (not committed)
- Add FuzzUpdate to internal/changelog and FuzzWriteVersion to
  internal/node to complete fuzz coverage for all file-rewriting packages
- Add fuzzing completeness guidelines to CLAUDE.md: authoritative table,
  exempt-package rationale, seed corpus rules

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/hugo.toml

@@ -0,0 +1,21 @@
+baseURL = "/"
+title = "releaser"
+theme = "geekdoc"
+
+pygmentsUseClasses = true
+pygmentsCodeFences = true
+
+[markup]
+  [markup.goldmark.renderer]
+    unsafe = true
+  [markup.tableOfContents]
+    startLevel = 1
+    endLevel = 9
+
+[params]
+  geekdocRepo = "https://git.k3nny.fr/releaser"
+  geekdocEditPath = "edit/main/docs/content"
+  geekdocSearch = true
+  geekdocMenuBundle = true
+  geekdocBreadcrumb = false
+  geekdocToC = true