Preserve runtime dir across restart so reconcile re-finds VMs

v0.1.4 fixed the binary-level reconcile path for jailer'd VMs but
left a hole at the systemd layer: bangerd.service and bangerd-root.service
both defaulted to RuntimeDirectoryPreserve=no, so /run/banger was
wiped on every daemon stop. The api-sock symlinks the helper creates
for live VMs (`/run/banger/fc-<id>.sock` → `<chroot>/firecracker.socket`)
went with it, and findByJailerPidfile — which derives the chroot
from the symlink target — couldn't resolve them. Reconcile then fell
through to "stale_vm" and tore down the surviving FC's dm-snapshot.

Add RuntimeDirectoryPreserve=yes to both unit templates so the
symlinks survive the restart window. Live-verified end-to-end on
the dev host: started a VM under v0.1.5, restarted helper +
daemon, confirmed the FC PID was unchanged and `banger vm ssh`
returned the same boot_id pre and post.

Daemon-lifecycle tests updated to assert the new directive is
present in both rendered units so future regressions show up at
test time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -10,6 +10,27 @@ changed between versions.
 
 ## [Unreleased]
 
+## [v0.1.6] - 2026-04-29
+
+### Fixed
+
+- v0.1.4's "running VMs survive daemon restart" fix was incomplete:
+  the binary-level reconcile path was correct, but `/run/banger` (the
+  daemon's runtime dir) was being wiped on every daemon stop because
+  systemd defaults to `RuntimeDirectoryPreserve=no`. The api-sock
+  symlinks the helper had created for live VMs vanished with it,
+  and `findByJailerPidfile` couldn't resolve them to find the chroot
+  + pidfile. v0.1.6 sets `RuntimeDirectoryPreserve=yes` on both
+  unit templates so the symlinks (and helper RPC sock) survive
+  the restart window. Live-verified: FC PID and guest boot_id both
+  unchanged across a full helper+daemon restart cycle with a VM
+  running.
+- v0.1.4's CHANGELOG correction stands: existing v0.1.x installs
+  (where x < 6) need a one-time `sudo banger system install` after
+  updating to v0.1.6 to pick up both the new `KillMode=process` and
+  the new `RuntimeDirectoryPreserve=yes` directives. `banger update`
+  swaps binaries, not unit files.
+
 ## [v0.1.5] - 2026-04-29
 
 No functional changes. Verification release for v0.1.4: the previous
@@ -193,7 +214,8 @@ root filesystem and network, and exits on demand.
   the swap rather than starting up against an incompatible store.
 - Linux only. amd64 only. KVM required.
 
-[Unreleased]: https://git.thaloco.com/thaloco/banger/compare/v0.1.5...HEAD
+[Unreleased]: https://git.thaloco.com/thaloco/banger/compare/v0.1.6...HEAD
+[v0.1.6]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.6
 [v0.1.5]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.5
 [v0.1.4]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.4
 [v0.1.3]: https://git.thaloco.com/thaloco/banger/releases/tag/v0.1.3