Implement XBPS proof of concept (issue #83)

Prove signed XBPS installation and immediate updates through Gitea.

Changes:
- Add scripts/xbps-publish.sh for automated XBPS publication
- Add Makefile targets: package-xbps, sign-xbps, xbps-publish
- Add docs/spec/xbps-proof-results.md with acceptance criteria results
- Add docs/adr/0008-native-void-support.md (architecture decision)
- Add docs/spec/native-void-support.md (feature specification)
- Add docs/spec/native-void-tickets.md (implementation tickets)

Proof results:
- Raw URL delivery verified (no LFS indirection)
- Signing key handling established (SSH RSA via xbps-rindex)
- Install and update flow demonstrated (v0.3.5 → v0.3.6)
- Cache behavior documented (6-hour max-age, -S flag for immediate discovery)
- Publication mechanism documented and automated
- Failure recovery demonstrated (git revert)

Repository: https://git.bongbetic.com/xavierk/Fenris-xbps

Co-authored-by: CommandCodeBot <noreply@commandcode.ai>

docs/spec/native-void-tickets.md

@@ -0,0 +1,71 @@
+# Native Void implementation tickets
+
+Status: Approved and published as Gitea issues 83–87 with native blocking edges and ready-for-agent labels. Parent specification: https://git.bongbetic.com/xavierk/Fenris/issues/82.
+
+Each issue references the published native Void specification, which includes ADR 0008. Existing Debian/RPM behavior, observation-history preservation, narrowly scoped privilege, and independent publication gates apply throughout.
+
+Published tickets: [1](https://git.bongbetic.com/xavierk/Fenris/issues/83), [2](https://git.bongbetic.com/xavierk/Fenris/issues/84), [3](https://git.bongbetic.com/xavierk/Fenris/issues/85), [4](https://git.bongbetic.com/xavierk/Fenris/issues/86), [5](https://git.bongbetic.com/xavierk/Fenris/issues/87).
+
+## 1. Prove signed XBPS installation and immediate updates through Gitea
+
+Blocked by: None.
+
+Deliver a dedicated public Gitea distribution repository and a repeatable, isolated XBPS-client proof using clearly identified test artifacts, without representing them as a validated Fenris release.
+
+- Verify permanent raw URL delivery of index, package and signature bytes without LFS indirection.
+- Establish signing-key handling and trust verification without exposing private keys.
+- Demonstrate install and update with a client that fetched the old index immediately before publication.
+- Resolve actual cache behavior and verify binary size limits; escalate any hosting change outside the agreed Gitea scope.
+- Publish index/artifacts together with serialized updates, preserve older downloadable artifacts, and demonstrate safe failure recovery.
+- Record results and the usable publication mechanism for subsequent tickets.
+
+## 2. Run and control Fenris monitoring natively under runit
+
+Blocked by: None.
+
+Deliver an end-to-end native monitoring path with existing CLI/TUI controls and truthful status in an isolated Void environment.
+
+- Scheduled and on-demand collection use the same acquisition path with no overlap and bounded execution.
+- Preserve cadence, initial boot delay, recovery after failures, and no catch-up semantics.
+- Resume/pause preserve monitoring-period bookkeeping and boot/runtime distinctions; raw service stops do not record deliberate disable.
+- Verify effective authentication and actionable native diagnostics, including missing-agent failures.
+- Preserve systemd behavior and application feature parity through existing public behavior tests.
+
+## 3. Install, upgrade and remove Fenris with native XBPS packages
+
+Blocked by: 2.
+
+Deliver buildable x86_64/glibc XBPS artifacts with dependency resolution and tested package lifecycle in an isolated Void environment.
+
+- Fresh install remains dormant; native controls enable monitoring afterward.
+- Package ownership, configuration preservation, permissions, and group access support real CLI/TUI reads and collector writes.
+- Upgrade snapshots and migrates observation history safely without recording a deliberate pause.
+- Removal performs sanctioned pause and retains history; reinstall and documented snapshot rollback behave correctly.
+- Installation over incompatible unmanaged remnants fails with a useful migration path.
+- Capture explicit lifecycle test results and verify Debian/RPM regressions relevant to changed packaging.
+
+## 4. Publish validated package formats independently from the release workflow
+
+Blocked by: 1, 3.
+
+Deliver a release workflow that builds, validates, signs and publishes XBPS alongside existing Debian/RPM support with independent format gates.
+
+- Unvalidated formats remain withheld while validated formats can ship.
+- Notes accurately identify available and withheld formats; source version, notes, checksums and artifacts agree.
+- A withheld format can be added after validation without replacing existing published artifacts.
+- Gitea serves every download; XBPS uses the proven permanent repository URL and immediate-refresh behavior.
+- Release failure/concurrency cannot expose an index referencing missing artifacts or erase the prior usable channel.
+- Host acceptance remains a required XBPS release gate, not bypassed by build/signature success.
+
+## 5. Validate and release on the user's Void machine
+
+Blocked by: 4.
+
+Deliver recorded host acceptance and the validated XBPS release, ending with Fenris installed and monitoring.
+
+- Recheck host state, identify/configure the intended NVMe drive, and preserve pre-existing data before package lifecycle operations.
+- Verify real acquisition, authenticated controls, scheduling, failure reporting, full dashboard behavior, and pause/resume semantics.
+- Coordinate and verify reboot persistence; absence of the reboot test leaves that gate pending.
+- Verify native upgrade/removal/reinstall with history preservation and immediate update discovery through Gitea.
+- Publish only after the XBPS gate passes, then verify downloads and released-package installation.
+- Preserve acceptance-test observation history and leave the released package monitoring; document installation, trust setup, diagnostics and rollback for Void users.