Add Markdown index HTML output mode

docs/operations.md

@@ -26,6 +26,12 @@ Run the local HTML publication:
 go run ./cmd/distributor run --config examples/local-html.yml
 ```
 
+Run the local `index.html` publication:
+
+```sh
+go run ./cmd/distributor run --config examples/local-index.yml
+```
+
 Preview local fan-out publication:
 
 ```sh
@@ -115,6 +121,37 @@ go run ./cmd/distributor validate <bundle-path>
 
 Use repeated `--file` flags to preserve a specific file order. If no `--file` flags are provided, the command scans the bundle directory recursively using the same filtering rules as `pkg/bundle.BuildManifest`.
 
+## Static HTML Publication
+
+Markdown-to-HTML publication can write sidecar files or a fixed `index.html`.
+
+Use sidecar mode when each Markdown source should keep a matching HTML filename:
+
+```yaml
+publish:
+  source: false
+  html: true
+transform:
+  markdown_to_html:
+    enabled: true
+    mode: sidecar
+```
+
+Use index mode for static-site destinations that should serve a bundle through `index.html`:
+
+```yaml
+publish:
+  source: false
+  html: true
+transform:
+  markdown_to_html:
+    enabled: true
+    mode: index
+    input: report.md
+```
+
+If `input` is omitted in index mode, the source manifest must list exactly one Markdown file. Generated HTML is recorded in `.distributor.json` with `kind: generated`, `source_path`, `transform: markdown_to_html`, digest, and size metadata.
+
 ## Source Validation and Inspection
 
 `validate` and `inspect` can operate on a local path or on one configured pipeline source. Configured source mode requires both `--config` and `--pipeline`; it loads the normal config, resolves `secrets.directory`, opens only the selected source backend, and does not open any destinations.