docs: update README, Windows plan, and launch drafts for Windows support

- README: platform-specific Quick Start, install/uninstall table
- Windows plan: Phase 2 complete, Phase 3 scoped
- Launch drafts: updated "Does it support Windows?" response

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/implementation/windows-support-plan.md

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+# Windows Support — Implementation Plan
+
+*March–April 2026*
+
+## Phase 1: Run on Windows without system integration — DONE (v0.3.0)
+
+- [x] Cross-platform `config_dir()` and `data_dir()`
+- [x] `src/system_dns.rs` — Windows DNS discovery via `ipconfig /all`
+- [x] Stubs for install/uninstall/service on unsupported OS
+- [x] Multicast LAN discovery (`SO_REUSEPORT` skipped on Windows)
+- [x] All deps compile on windows-msvc
+- [x] CI: `check-windows` job (build + clippy)
+- [x] Cross-platform LAN discovery tested: macOS ↔ Windows
+
+## Phase 2: DNS configuration — DONE (PR #28)
+
+- [x] `numa install` — set DNS to 127.0.0.1 via `netsh` for all active interfaces
+- [x] `numa uninstall` — restore DNS from backup (DHCP or static with secondaries)
+- [x] `ipconfig /all` parser — per-interface adapter name, DHCP status, DNS servers
+- [x] Localization — German adapter/DHCP/DNS labels handled
+- [x] Disconnected adapters — skipped
+- [x] Backup — `%PROGRAMDATA%\numa\original-dns.json`
+- [x] Dnscache — disable via registry on install, re-enable on uninstall (reboot required)
+- [x] Auto-start — registry Run key (`HKLM\...\Run\Numa`) on install, removed on uninstall
+- [x] UDP ConnectionReset — Windows ICMP error 10054 caught and ignored
+- [x] IP validation — added to `discover_windows()`
+- [x] CI: `cargo test` + binary artifact upload on Windows
+- [ ] `README.md` — add Windows install instructions
+
+## Phase 3: Full service integration (future)
+
+### Windows Service
+
+- Use `windows-service` crate to register Numa as a Windows Service
+- `sc.exe create numa binPath=...` as alternative
+- Auto-start on boot (SYSTEM context, no login required), auto-restart on crash
+- Replace registry Run key with proper SCM integration
+
+### CA trust
+
+- `certutil.exe -addstore Root ca.pem` to trust Numa CA system-wide
+- Reverse: `certutil.exe -delstore Root "Numa Local CA"`
+- Needs admin elevation
+
+### DHCP DNS detection
+
+- Current `detect_dhcp_dns()` returns `None` on Windows
+- Could parse `ipconfig /all` for "DHCP Server" + "DNS Servers" lines
+- Or use WinAPI `GetNetworkParams()`