system: prototype self-hosted native builds

docs/PROGRESS.md

@@ -42,6 +42,10 @@ Fruix currently has:
   - real XCP-ng boot of a development-enabled Fruix system
   - in-guest `buildworld` / `buildkernel`
   - staged `installworld` / `distribution` / `installkernel`
+- a validated controlled guest self-hosted native base-build prototype via:
+  - `/usr/local/bin/fruix-self-hosted-native-build`
+  - result roots under `/var/lib/fruix/native-builds`
+  - in-guest source recovery from current-system metadata
 
 Validated boot modes still are:
 
@@ -54,33 +58,32 @@ The validated Phase 18 installation work currently uses:
 
 ## Latest completed achievement
 
-### 2026-04-05 — Phase 20.2 completed
+### 2026-04-05 — Phase 20.3 completed
 
-Fruix now has a validated intermediate path where the host still orchestrates the workflow, but real FreeBSD native base-build work runs inside a booted Fruix-managed FreeBSD guest.
+Fruix now has a validated first controlled guest self-hosted native base-build prototype, on top of the already validated host-initiated in-guest build path.
 
 Highlights:
 
-- development-enabled systems now expose canonical native-build compatibility links at:
-  - `/usr/include -> /run/current-system/development-profile/usr/include`
-  - `/usr/share/mk -> /run/current-system/development-profile/usr/share/mk`
-- media builder versions were bumped so booted images and future installed targets pick up that rootfs layout change
-- the validated guest build path now runs real FreeBSD native build steps inside the Fruix-managed guest:
-  - `buildworld`
-  - `buildkernel`
-  - `installworld`
-  - `distribution`
-  - `installkernel`
-- staged install steps use:
-  - `DB_FROM_SRC=yes`
-  - so the staged install is driven by the declared source tree's account database rather than by the guest's minimal local `/etc` state
-- the validated result now includes staged native artifact outputs for:
+- development-enabled systems now ship an in-guest helper at:
+  - `/usr/local/bin/fruix-self-hosted-native-build`
+- the helper recovers the declared materialized FreeBSD source store from:
+  - `/run/current-system/metadata/store-layout.scm`
+- the helper records self-hosted build results under:
+  - `/var/lib/fruix/native-builds/<run-id>`
+  - `/var/lib/fruix/native-builds/latest`
+- heavy object/stage work remains under:
+  - `/var/tmp/fruix-self-hosted-native-builds/<run-id>`
+- the prototype exposed an important contract detail:
+  - a naive reuse of the development-shell exports polluted `buildworld`
+  - the validated helper therefore sanitizes development-oriented variables such as `MAKEFLAGS`, `CPPFLAGS`, `CFLAGS`, `CXXFLAGS`, and `LDFLAGS` before world/kernel bootstrap
+- the validated result includes guest-recorded native artifact outputs for:
   - kernel
   - bootloader slice
   - headers / `usr/share/mk`
 
 Validation:
 
-- `PASS phase20-host-initiated-native-build-xcpng`
+- `PASS phase20-self-hosted-native-build-xcpng`
 
 Reports:
 
@@ -88,6 +91,7 @@ Reports:
 - `docs/GUIX_DIFFERENCES.md`
 - `docs/reports/phase20-development-environment-freebsd.md`
 - `docs/reports/phase20-host-initiated-native-builds-freebsd.md`
+- `docs/reports/phase20-self-hosted-native-builds-freebsd.md`
 
 ## Recent major milestones
 
@@ -111,8 +115,11 @@ Reports:
 
 ## Next step
 
-Per `docs/PLAN_4.md`, the next planned step is:
+`docs/PLAN_4.md` currently ends at Phase 20.3, and that milestone sequence is now complete.
 
-- **Phase 20.3** — reassess and potentially prototype guest self-hosted base builds
+The next practical follow-up is therefore no longer another planned `PLAN_4` phase, but a product decision:
 
-Phase 20.2 is now complete: Fruix validates host-initiated native FreeBSD base builds running inside the approved real XCP-ng Fruix guest path.
+- whether to keep the new guest self-hosted helper as a narrow prototype while Phase 20.2 remains the default operator path
+- or whether to invest in a broader guest-driven Fruix-native native-build workflow
+
+Phase 20.3 is now complete: Fruix validates a first controlled guest self-hosted native FreeBSD base-build prototype on the approved real XCP-ng path.