docs(k8s): add Talos architecture, distro decision, and bootstrap plan

Author the docs/k8s/ directory capturing the pfv-k8s control-plane design:

- README.md: TL;DR of all decisions (distro, runtime, cnode count, admin
  access, identity, tenancy, registry, storage)
- DISTRO-DECISION.md: Talos vs k3s analysis. Recommend Talos because the
  ITAR/classified requirement makes its immutable, API-only, measured-boot
  posture structurally easier to certify than SCAP-hardened Debian. k3s was
  only ever a plan (no cluster deployed), so cutover cost is ~zero.
- ARCHITECTURE.md: target arch with mermaid diagrams covering control
  plane, LAN-only network with Tailscale subnet-router admin, Cilium CNI,
  OIDC to Keycloak, per-tenant vcluster isolation (incl. ITAR tenant),
  Harbor pull-through cache on D3 SSD, bootstrap sequence, and DR.

Gardening: register docs/k8s/ in docmap.md, update STATUS.md with the new
k8s section and the three pending user decisions (cnode count, host spread,
Tailscale pattern).

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STATUS.md

@@ -35,6 +35,16 @@ infrastructure, and Proxmox cluster ops.
 - [ ] tsys5: blocked on 2nd ethernet cable + NVMe install
 - [ ] tsys2: pending rebuild from Win10 to Proxmox
 
+### Kubernetes Architecture (docs authored, pending implementation)
+- [x] `docs/k8s/` created: README, DISTRO-DECISION, ARCHITECTURE
+- [x] Distro decision: **Talos Linux** (over k3s), driven by ITAR/classified
+  requirement. Immutable + API-only + measured-boot = structurally stronger
+  compliance posture than SCAP-hardened Debian.
+- [x] Target arch documented: 3 cnodes (local-lvm boot), Cilium CNI, vcluster
+  per tenant, Harbor pull-through cache on D3 SSD, OIDC→Keycloak (Cloudron),
+  Tailscale subnet-router for admin (cluster nodes LAN-only, zero egress).
+- [ ] 3 decisions pending user confirm (see Pending below)
+
 ### Repo Merge
 - [x] KNELServerBuild merged into PFVCluster (history preserved)
 - [x] Directory structure reorganized (provisioning/, tests/, perf/, docs/)
@@ -50,10 +60,17 @@ infrastructure, and Proxmox cluster ops.
 
 ## Pending (next session priorities)
 
-1. Provisioning: add `tailscale up --accept-dns=false` after resolv.conf deploy
-2. DNS: verify Pi-hole forwards knel.net to local Technitium on both nodes
-3. Perf: complete tsys4/5 tuning after hardware install (Friday)
-4. tsys2: rebuild from Win10 to Proxmox (k8s-dedicated host)
+1. **k8s: confirm 3 decisions** before bootstrap:
+   - Cnode count: 3 (recommended) vs 5
+   - Cnode host spread: tsys9 + tsys1 + tsys3 (recommended, 3-host, local-lvm)
+   - Tailscale pattern: subnet router on `tailscale-router` (recommended)
+2. Provisioning: add `tailscale up --accept-dns=false` after resolv.conf deploy
+3. DNS: verify Pi-hole forwards knel.net to local Technitium on both nodes
+4. Perf: complete tsys4/5 tuning after hardware install (Friday)
+5. tsys2: rebuild from Win10 to Proxmox (k8s-dedicated host)
+6. **k8s deferred topics** (tracked for future sessions): ETL tooling
+   (GDAL/PostGIS/xarray/Dask → RWX vs RWO), HPC scheduler (Argo/Volcano),
+   per-tenant vcluster policy templates, solar-aware scale-out
 
 ## Infrastructure Summary