Add destination link metadata

docs/config.md

@@ -117,6 +117,28 @@ Fixed destinations select the newest discovered source bundle by manifest `creat
 
 Fixed mapping is useful for stable latest-style paths. It is more destructive than archive-style publication because successive source bundles target the same destination root. Preview fixed destinations with `run --dry-run`, especially before using `--force`.
 
+## Destination Links
+
+Destinations can record public URLs for published outputs:
+
+```yaml
+links:
+  base_url: https://reports.example.com/archive
+  primary: auto
+```
+
+`links.base_url` is an absolute `http` or `https` URL corresponding to the destination backend root. It may include a path prefix, but it must not include a query string or fragment. Distributor does not infer public URLs from backend config.
+
+`links.primary` selects the top-level primary URL stored in destination state:
+
+- `auto`: prefer `index.html`, then generated HTML, then source outputs.
+- `html`: use the first generated HTML output.
+- `source`: use the first copied source output.
+
+If a destination has no `links` block, no URL metadata is generated. If a primary policy has no matching output, per-output URLs are still recorded and the top-level primary URL is omitted.
+
+Output URLs are built from `links.base_url`, the destination bundle path, and the output path using URL path semantics. `index.html` outputs produce directory-style URLs that omit the filename.
+
 ## Reference
 
 Top level:
@@ -156,6 +178,8 @@ Destination:
 - `publish`: optional; defaults to source-only publication.
 - `transform`: required only for generated HTML publication.
 - `path_mapping.mode`: optional; defaults to `preserve_relative`. Accepted values are `preserve_relative` and `fixed`.
+- `links.base_url`: optional links block; when present, `base_url` is required and must be an absolute HTTP or HTTPS URL without query string or fragment.
+- `links.primary`: optional; defaults to `auto`. Accepted values are `auto`, `html`, and `source`.
 - `transfer`: optional; defaults described below.
 
 Accepted backend names:
@@ -246,6 +270,7 @@ Defaults are applied after YAML decoding and before validation:
 - `publish.source: true`
 - `publish.html: false`
 - `path_mapping.mode: preserve_relative`
+- `links.primary: auto` when a `links` block is present and `primary` is omitted
 - `transfer.on_destination_same: skip`
 - `transfer.on_destination_older: replace`
 - `transfer.on_destination_newer: skip`