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/content/installation.md

@@ -0,0 +1,59 @@
+---
+title: Installation
+weight: 10
+---
+
+## Pre-built binaries
+
+Download the latest release for your platform from the [Releases page](https://git.k3nny.fr/releaser/releases).
+
+```bash
+# Linux (amd64)
+curl -sSL https://git.k3nny.fr/releaser/releases/download/v1.5.0/releaser-v1.5.0-linux-amd64 \
+  -o /usr/local/bin/releaser
+chmod +x /usr/local/bin/releaser
+```
+
+Available platforms: `linux-amd64`, `linux-arm64`, `darwin-amd64`, `darwin-arm64`, `windows-amd64.exe`.
+
+## Docker
+
+```bash
+docker pull git.k3nny.fr/releaser/releaser:latest
+
+# Run in the current repository
+docker run --rm \
+  -v "$PWD:/repo" \
+  -e GITLAB_TOKEN="$GITLAB_TOKEN" \
+  git.k3nny.fr/releaser/releaser:latest
+```
+
+## Build from source
+
+Requires Go 1.21+.
+
+```bash
+git clone https://git.k3nny.fr/releaser/releaser.git
+cd releaser
+go build -o /usr/local/bin/releaser ./cmd
+```
+
+## Verify
+
+```bash
+releaser --version
+```
+
+## First run
+
+Scaffold a default `.releaser.yml` in your repository root:
+
+```bash
+releaser --init
+```
+
+Then do a dry run to check the version that would be produced:
+
+```bash
+releaser --dry-run
+```