Add fixed destination path mapping

docs/config.md

@@ -83,6 +83,40 @@ transform:
 
 When `mode: index` omits `input`, the source manifest must list exactly one Markdown file.
 
+## Destination Path Mapping
+
+Each destination chooses how source bundle paths map into that destination:
+
+```yaml
+path_mapping:
+  mode: preserve_relative
+```
+
+`preserve_relative` is the default. It publishes each discovered source bundle at the same path relative to the destination backend root. A source bundle at `daily/2026-06-01` publishes below `daily/2026-06-01` for that destination.
+
+`fixed` publishes one selected source bundle directly at the destination backend root:
+
+```yaml
+destinations:
+  - id: latest-html
+    backend: local
+    path: /srv/www/reports/latest
+    path_mapping:
+      mode: fixed
+    publish:
+      source: false
+      html: true
+    transform:
+      markdown_to_html:
+        enabled: true
+        mode: index
+        input: report.md
+```
+
+Fixed destinations select the newest discovered source bundle by manifest `created` timestamp. If multiple candidates have the same timestamp, the source-root-relative bundle path in ascending order wins. Older candidates are not planned or written for that destination.
+
+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`.
+
 ## Reference
 
 Top level:
@@ -121,6 +155,7 @@ Destination:
 - Backend fields: same accepted shape as source backends, with destination fields at the destination level.
 - `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`.
 - `transfer`: optional; defaults described below.
 
 Accepted backend names:
@@ -210,6 +245,7 @@ Defaults are applied after YAML decoding and before validation:
 - `transform.markdown_to_html.mode: sidecar` when a Markdown-to-HTML transform block is present and mode is omitted
 - `publish.source: true`
 - `publish.html: false`
+- `path_mapping.mode: preserve_relative`
 - `transfer.on_destination_same: skip`
 - `transfer.on_destination_older: replace`
 - `transfer.on_destination_newer: skip`
@@ -242,5 +278,6 @@ Maintained examples live under [examples](../examples/):
 - `local-html.yml`: runnable local HTML publication.
 - `local-index.yml`: runnable local `index.html` publication.
 - `fan-out.yml`: runnable local fan-out publication to source and HTML destinations.
+- `archive-and-latest.yml`: runnable local fan-out publication to an archive destination and a fixed latest destination.
 - `ssh-destination.yml`: environment-gated local-to-SSH publication example.
 - `s3-destination.yml`: environment-gated local-to-S3 publication example.