Add Fruix bootable installer environment

docs/PROGRESS.md

@@ -1,5 +1,97 @@
 # Progress
 
+## 2026-04-04 — Phase 18.2 completed: Fruix now boots a minimal installer environment and installs a target system from inside it
+
+Completed work:
+
+- added in `modules/fruix/system/freebsd.scm`:
+  - `installer-operating-system`
+  - `operating-system-installer-image-spec`
+  - `materialize-installer-image`
+- the installer environment is now derived from the selected target operating system, while forcing the currently most stable installer boot path:
+  - `freebsd-init+rc.d-shepherd`
+- the installer image now carries:
+  - its own installer-system closure
+  - the selected target-system closure
+  - the selected target-system store closure
+  - a staged target rootfs under:
+    - `/var/lib/fruix/installer/target-rootfs`
+  - installer plan/state files under:
+    - `/var/lib/fruix/installer`
+  - installer helper scripts:
+    - `/usr/local/libexec/fruix-installer-run`
+    - `/usr/local/etc/rc.d/fruix-installer`
+- the booted installer environment now performs the install from inside the guest by:
+  - partitioning the selected target disk
+  - creating EFI + UFS filesystems
+  - copying the staged target rootfs
+  - copying only the selected target system's required store items into the target `/frx/store`
+  - installing the target `loader.efi`
+  - writing target install metadata to:
+    - `/var/lib/fruix/install.scm`
+  - recording installer state in:
+    - `/var/lib/fruix/installer/state`
+  - logging to:
+    - `/var/log/fruix-installer.log`
+- added user-facing CLI support in `scripts/fruix.scm`:
+  - `fruix system installer`
+  - new option:
+    - `--install-target-device DEVICE`
+- corrected the default FreeBSD virtio install target device for QEMU validation to:
+  - `/dev/vtbd1`
+  rather than the earlier incorrect Linux-flavored guess:
+  - `/dev/vtblk1`
+- fixed `materialize-bhyve-image` so the generated UFS filesystem label now respects:
+  - `root-partition-label`
+  rather than always hardcoding:
+  - `fruix-root`
+- added validation artifacts:
+  - `tests/system/phase18-installer-target-operating-system.scm.in`
+  - `tests/system/run-phase18-installer-environment.sh`
+- wrote:
+  - `docs/reports/phase18-installer-environment-freebsd.md`
+
+Validation:
+
+- `PASS phase18-installer-environment`
+- regression re-checks:
+  - `PASS phase18-system-install`
+  - `PASS phase17-source-revisions-qemu`
+- validated a full two-disk workflow:
+  - booted Fruix installer image under QEMU/UEFI/TCG
+  - installer environment became reachable over SSH
+  - installer environment completed in-guest install with:
+    - `installer_state=done`
+  - installer log recorded:
+    - `fruix-installer:done`
+  - installed target disk contained:
+    - GPT partition table
+    - ESP filesystem:
+      - `msdosfs`
+    - root filesystem:
+      - `ufs`
+    - `EFI/BOOT/BOOTX64.EFI`
+    - `/var/lib/fruix/install.scm`
+- validated source-driven provenance through the installer environment from:
+  - Git ref:
+    - `stable/15`
+  - pinned commit:
+    - `332708a606f6bf0841c1d4a74c0d067f5640fe89`
+  - materialized source store:
+    - `/frx/store/7563df2714ae7fa9bd40b83c74512ffe2cb2ad91b297915591b55c76edbb2fcb-freebsd-source-stable15-installer-target-source`
+- validated boot of the installed target after in-guest installation:
+  - `/run/current-system` points at the installed target closure
+  - `/usr/local/etc/rc.d/fruix-shepherd onestatus` reports running
+  - `sshd` running
+  - activation completed successfully
+
+Current assessment:
+
+- Phase 18.2 is complete
+- Fruix now has a minimal Fruix-managed installer environment, not just a host-driven installation primitive
+- the next step is Phase 18.3:
+  - produce a bootable installer ISO for UEFI systems
+
 ## 2026-04-03 — Phase 18.1 completed: Fruix now has a minimal non-interactive installation flow
 
 Completed work: