docs: add Void installation and operations guide

README.md

@@ -2,7 +2,7 @@
 
 *Observes an NVMe drive's real-world use and translates that history into an understandable endurance outlook.*
 
-Fenris is a persistent TUI monitor backed by a short-lived privileged collector on a systemd timer. It reads SMART data every few minutes, stores compact observation history in SQLite, and recomputes a usage-adjusted theoretical lifespan on every screen render — no fairy dust, just your actual bytes.
+Fenris is a persistent TUI monitor backed by a short-lived privileged collector on the host's native scheduler. It reads SMART data every few minutes, stores compact observation history in SQLite, and recomputes a usage-adjusted theoretical lifespan on every screen render — no fairy dust, just your actual bytes.
 
 ---
 
@@ -10,7 +10,7 @@ Fenris is a persistent TUI monitor backed by a short-lived privileged collector
 
 - **Python ≥ 3.10** (verified at install time)
 - **smartmontools** (`smartctl` — verified at install time)
-- **systemd** with a polkit agent (the collector runs as root oneshot; elevation is exclusively polkit)
+- **systemd** or **runit**, with a polkit agent (the collector runs as root; elevation is exclusively polkit)
 
 No other OS packages or Python dependencies beyond [Textual](https://textual.textualize.io/) (pinned in the lockfile).
 
@@ -66,6 +66,36 @@ The repo file sets `gpgcheck=1` against the Fenris packaging key (downloaded
 from the raw URL in `gpgkey`) and `repo_gpgcheck=0` (metadata check left to
 TLS).
 
+### Void Linux (XBPS)
+
+Void x86_64 with glibc and runit is the native target. Its XBPS channel is
+withheld until the host-acceptance gate passes; do not install proof artifacts
+from it. Once a Fenris Release lists XBPS as available, add the permanent
+signed repository, refresh its metadata, and install the package:
+
+```bash
+sudo install -d -m 0755 /etc/xbps.d
+echo 'repository=https://git.bongbetic.com/xavierk/Fenris-xbps/raw/branch/stable/x86_64' \
+  | sudo tee /etc/xbps.d/fenris.conf
+sudo xbps-install -S fenris
+```
+
+XBPS requires remote repositories to be signed. On the first refresh it
+displays the repository signing key embedded in the signed metadata; accept it
+only when its RSA SHA256 fingerprint is
+`SHA256:kC1+z5Z9OtW5qcoXcV7sxr7m1wEvxbTUgRxd9Yib/Qk`. The public key is also
+available at
+`https://git.bongbetic.com/xavierk/Fenris-xbps/raw/branch/stable/keys/fenris-xbps-signing.pub`.
+For later updates, always refresh first so XBPS fetches the current index:
+
+```bash
+sudo xbps-install -Syu
+```
+
+The runit service remains dormant after installation. `fenris monitor resume`
+creates `/var/service/fenris-collect`; pause removes that link and records a
+deliberate disable in the observation history.
+
 ### Package signature verification
 
 The RPM payload is signed with the Fenris packaging key (RSA 3072).
@@ -84,12 +114,12 @@ The packaging public key is published in-repo — no keyservers. See
 
 ### Dormant install
 
-A fresh package install is fully dormant. Units are present but disabled;
-nothing runs. The only opt-in is the sanctioned toggle:
+A fresh package install is fully dormant. Its native scheduler is present but
+disabled; nothing runs. The only opt-in is the sanctioned toggle:
 
 ```bash
-fenris monitor resume    # enable timer + open first monitoring period
-fenris monitor pause     # close the period, disable timer
+fenris monitor resume    # enable scheduling + open first monitoring period
+fenris monitor pause     # close the period, disable scheduling
 ```
 
 ## Development install (make install)
@@ -117,6 +147,7 @@ make purge           # also removes /etc/fenris and /var/lib/fenris
 ```bash
 sudo apt update && sudo apt upgrade fenris    # Debian/Ubuntu
 sudo dnf upgrade fenris                       # Fedora
+sudo xbps-install -Syu                        # Void Linux
 ```
 
 ### Development upgrade
@@ -133,6 +164,12 @@ What it does:
 5. Applies forward-only schema migrations (the store directory is never rebuilt; automatic downgrade does not exist).
 
 Rollback: reinstall the previous version and restore `observations.db.bak`.
+On Void, pause monitoring first, copy the compatible snapshot back to
+`/var/lib/fenris/observations.db`, then force-install the matching older
+package version. If that version is no longer indexed, add its retained XBPS
+archive to a local repository with `xbps-rindex -a` and use
+`xbps-install -R <local-repository> -f fenris-<version>`. Installing an older
+package over a newer observation store is unsupported.
 
 ## Migration from make install
 
@@ -150,6 +187,7 @@ continuity. Over-installing the package over a `make install` is
 sudo apt remove fenris       # preserves config and store
 sudo apt purge fenris        # also removes config and store
 sudo dnf remove fenris       # preserves config and store
+sudo xbps-remove fenris      # preserves config and store
 ```
 
 ### Development removal
@@ -174,6 +212,19 @@ sudo systemctl edit fenris-collect.timer
 
 No interval key exists in `/etc/fenris/fenris.conf`. Cadence is a systemd concern, not a Fenris configuration key.
 
+On Void, Fenris uses its native runit service instead: its initial collection
+is delayed by two minutes and later collections run five minutes after the
+previous run finishes. Inspect its state and diagnostics with:
+
+```bash
+sv status fenris-collect
+sudo tail -n 50 /var/log/fenris-collect/current
+```
+
+`fenris status` also reports the separate boot-enabled, runtime-active,
+collection outcome, and observation-store freshness facts. A failed collection
+is retried at the next interval; it never fabricates missing observations.
+
 ## CLI reference
 
 | Command | Behavior |
@@ -181,8 +232,8 @@ No interval key exists in `/etc/fenris/fenris.conf`. Cadence is a systemd concer
 | `fenris` | Opens the TUI (no arguments). |
 | `fenris status` | Projection facts, enabled/active state, last collect outcome, journal hint on failure or staleness. Never auto-samples. |
 | `fenris sample` | On-demand collection via the privileged helper. Blocks until the run completes. |
-| `fenris monitor pause` | Sanctioned disable — asks for confirmation, then disables the timer and closes the monitoring period. |
-| `fenris monitor resume` | Sanctioned enable — enables the timer and opens a monitoring period. No confirmation. |
+| `fenris monitor pause` | Sanctioned disable — asks for confirmation, then disables native scheduling and closes the monitoring period. |
+| `fenris monitor resume` | Sanctioned enable — enables native scheduling and opens a monitoring period. No confirmation. |
 | `fenris baseline set <json>` | CLI-side validation, then polkit-guarded persistence. |
 | `fenris baseline clear` | Remove the endurance baseline. |
 | `fenris import <path>` | Idempotent single-transaction legacy import. |