docs: roll README + CHANGELOG forward past v0.3.1

README:
- Status line bumped from v0.3.0 to v0.3.1 with the actually-validated
  framing (K8s Ready under QEMU virt+HVF, CoreDNS + local-path +
  nginx all Running) and a link to CHANGELOG.md for full notes.
- Roadmap: Phase 7 (generic ARM64) flipped to "Complete (v0.3.1, K8s
  Ready under QEMU virt+HVF)". OCI cosign verification, LABEL=KSOLODATA
  on ARM64, and real-hardware ARM64 validation move from "Planned for
  v0.3.1" to "Planned for v0.3.2" — they didn't make this release.

CHANGELOG:
- New "[Unreleased]" section covering the four post-v0.3.1 CI / repo
  housekeeping commits: drop tag trigger on build-arm64.yaml (04a5cd2),
  gitignore .env/credentials (48267e1), fix gated x86 job staying
  "queued" instead of "skipped" (fb24e64), and paths-ignore on
  build-arm64.yaml so workflow/docs-only commits skip the 60-minute
  kernel rebuild (e1b8a69).

No runtime changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -2,7 +2,7 @@
 
 An immutable, bootable Linux distribution purpose-built for [KubeSolo](https://github.com/portainer/kubesolo) — Portainer's ultra-lightweight single-node Kubernetes.
 
-> **Status (v0.3.0):** x86_64 and generic ARM64 (UEFI / virtio / mainline kernel) both build and boot end-to-end. Update agent has an explicit state machine, OCI registry distribution alongside HTTP, channel + maintenance-window + version-stepping-stone gates, and auto-rollback. ARM64 Raspberry Pi support remains paused pending physical hardware. See [docs/release-notes-0.3.0.md](docs/release-notes-0.3.0.md) for the full v0.3.0 changelog.
+> **Status (v0.3.1):** First fully-validated generic ARM64 release. x86_64 and ARM64 (UEFI / virtio / mainline kernel) both build and boot end-to-end; v0.3.1 closes the dual-glibc, nftables address-family, and kube-proxy expression-module gaps that kept v0.3.0 from reaching a Ready node on ARM64. Validated end-to-end under QEMU virt + HVF on Apple Silicon: `kubectl get nodes` reports `Ready`, CoreDNS, local-path-provisioner, and an nginx test workload all `Running`. The update agent has an explicit state machine, OCI registry distribution alongside HTTP, channel + maintenance-window + version-stepping-stone gates, and auto-rollback. ARM64 Raspberry Pi support remains paused pending physical hardware. See [CHANGELOG.md](CHANGELOG.md) for the full v0.3.1 changelog and [docs/release-notes-0.3.0.md](docs/release-notes-0.3.0.md) for the v0.3.0 milestone summary.
 
 ## What is this?
 
@@ -245,12 +245,12 @@ Metrics include: `kubesolo_os_info`, `boot_success`, `boot_counter`, `uptime_sec
 | 5 | CI/CD, OCI distribution, Prometheus metrics, ARM64 cross-compile | Complete |
 | 6 | Security hardening, AppArmor | Complete |
 | - | Custom kernel build for container runtime fixes | Complete (x86_64) |
-| 7 | ARM64 generic (mainline kernel, UEFI, virtio) | Complete (v0.3.0, QEMU validated) |
+| 7 | ARM64 generic (mainline kernel, UEFI, virtio) | Complete (v0.3.1, K8s Ready under QEMU virt+HVF) |
 | 8 | Update engine v2 (state machine, channels, OCI, pre-flight gates) | Complete (v0.3.0) |
 | - | ARM64 Raspberry Pi (custom kernel, firmware, SD card image) | Paused — needs hardware |
-| - | OCI cosign signature verification | Planned for v0.3.1 |
-| - | LABEL=KSOLODATA on ARM64 (replace blkid/findfs path) | Planned for v0.3.1 |
-| - | Real-hardware ARM64 validation (Graviton / Ampere) | Planned for v0.3.1 |
+| - | OCI cosign signature verification | Planned for v0.3.2 |
+| - | LABEL=KSOLODATA on ARM64 (replace blkid/findfs path) | Planned for v0.3.2 |
+| - | Real-hardware ARM64 validation (Graviton / Ampere) | Planned for v0.3.2 |
 
 ## License