docs: split project reports, pin checker links

Reading this project's own reports gets its own page. Checker code is linked at the revision each platform list was read from. Installer moves to Your setup, legal to Start here, build internals to Contribute, and Reference pages carry a group.

wiki/installer.md

@@ -1,6 +1,6 @@
 ---
-level: explore
-order: 30
+level: setup
+order: 100
 ---
 
 # All installer options
@@ -20,6 +20,13 @@ How the command protects your machine is under
 [Trust boundary](#trust-boundary). The BIOS folder of each setup is on
 [Get your files](../which-pack.md).
 
+## Options at a glance
+
+Read from the installer's own option list, the one `--help` prints. The
+[Options](#options) table below gives each one in full.
+
+<!-- installer-options -->
+
 ## One line
 
 ```bash
@@ -810,7 +817,7 @@ what it must hash to.
 Entries the collection cannot satisfy are not silently dropped: they travel in
 `omitted_files` with a reason, and the run prints the count before downloading
 anything. `not_found` means no file in the collection matches the entry, which
-is what the [gap analysis](../gaps.md) tracks.
+is what the gap analysis tracks (Reference: [What the packs do not hold](../gaps.md)).
 
 Some cores read a whole tree of data rather than a few files: Dolphin's `Sys/`,
 PPSSPP's assets, blueMSX's machines. These are not files of the collection, so
@@ -950,7 +957,7 @@ no event at all. A program reads a missing `end` as that case.
 
 | Variable | Effect |
 |----------|--------|
-| `RETROBIOS_REF` | Branch or tag the file list and the files committed to the repository are read from. Defaults to `main`. Files the manifest marks `release_asset` always come from the `large-files` release, whatever the ref, and that release replaces an asset in place when it is rebuilt. Each release deletes the previous release tags ([release process](release-process.md#cutting-a-release)), so a tag holds a file list until the next release |
+| `RETROBIOS_REF` | Branch or tag the file list and the files committed to the repository are read from. Defaults to `main`. Files the manifest marks `release_asset` always come from the `large-files` release, whatever the ref, and that release replaces an asset in place when it is rebuilt. Each release deletes the previous release tags, so a tag holds a file list until the next release. For contributors: [release process](release-process.md#cutting-a-release) |
 | `RETROBIOS_BASE_URL` | Base URL for the manifest and the files it declares. HTTPS only, plain HTTP allowed to loopback for end-to-end tests. Whoever controls this base controls the expected hashes, hence the check. A file list that cannot be fetched names the address, and this variable when it is set |
 | `RETROBIOS_OS` | Names the host outright (`linux`, `wsl`, `windows`, `darwin`, `android`) instead of detecting it |
 | `EXTERNAL_STORAGE` | Android only, the shared storage root RetroArch builds its default directories from. Defaults to `/storage/emulated/0` |