fix(robustness): null guard WMI reads, dispose SHA256, abort LSV2 timeout (ISS-001, ISS-005, ISS-006)

ISS-001: MachineFingerprint.GetFingerprint() — null-safe WMI property reads
  - processorID and SerialNumber accessed with ?. and ?? string.Empty
  - prevents NullReferenceException on machines with missing WMI properties

ISS-005: LicenseValidator.Validate() — SHA256CryptoServiceProvider in using block
  - disposed on all code paths (success and failure)

ISS-006: Lsv2Client.Connect() — close TcpClient on timeout
  - _tcp.Close() called when ConnectAsync.Wait() times out
  - aborts pending socket task instead of leaking thread-pool slot

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.paul/ROADMAP.md

@@ -165,7 +165,7 @@ Completed: 2026-05-18
 
 | Phase | Name | Plans | Status | Completed |
 |-------|------|-------|--------|-----------|
-| 13 | robustness-fixes | TBD | Not started | - |
+| 13 | robustness-fixes | 1 | Planning | - |
 | 14 | test-hardening | TBD | Not started | - |
 
 ### Phase 13: robustness-fixes

.paul/STATE.md

@@ -10,22 +10,23 @@ See: .paul/PROJECT.md (updated 2026-05-18)
 ## Current Position
 
 Milestone: v0.4 Robustness — **In Progress**
-Phase: 13 of 14 (robustness-fixes) — Not started
-Plan: Not started
-Status: Ready to plan
-Last activity: 2026-05-18 — Milestone v0.4 created
+Phase: 13 of 14 (robustness-fixes) — Planning
+Plan: 13-01 created, awaiting approval
+Status: PLAN created, ready for APPLY
+Last activity: 2026-05-18 — Created .paul/phases/13-robustness-fixes/13-01-PLAN.md
 
 Progress:
 - Milestone v0.1: [██████████] 100% (complete)
 - Milestone v0.2: [██████████] 100% (complete)
 - Milestone v0.3: [██████████] 100% (complete)
 - Milestone v0.4: [░░░░░░░░░░] 0%
+- Phase 13: [░░░░░░░░░░] 0%
 
 ## Loop Position
 
 ```
 PLAN ──▶ APPLY ──▶ UNIFY
-  ○        ○        ○     [Ready for Phase 13 PLAN]
+  ✓        ✓        ○     [Plan 13-01 applied, ready for UNIFY]
 ```
 
 ## What Was Built (v0.3 Code Quality — complete)
@@ -163,8 +164,8 @@ Documents: `.paul/codebase/` (7 files — STACK, ARCHITECTURE, STRUCTURE, CONVEN
 
 Last session: 2026-05-18
 Stopped at: v0.4 Robustness milestone created, ready to plan Phase 13
-Next action: /paul:plan — Phase 13 (robustness-fixes): ISS-001, ISS-005, ISS-006
-Resume file: .paul/ROADMAP.md
+Next action: Review and approve plan, then run /paul:apply .paul/phases/13-robustness-fixes/13-01-PLAN.md
+Resume file: .paul/phases/13-robustness-fixes/13-01-PLAN.md
 
 ---
 *STATE.md — Updated after every significant action*

Cnc/Heidenhain/Lsv2Client.cs

@@ -30,8 +30,12 @@ namespace NcProgramManager.Cnc.Heidenhain
             _tcp = new TcpClient();
             _tcp.SendTimeout    = (int)_config.ConnectTimeout.TotalMilliseconds;
             _tcp.ReceiveTimeout = (int)_config.ConnectTimeout.TotalMilliseconds;
-            if (!_tcp.ConnectAsync(_config.IpAddress, _config.Port).Wait(_config.ConnectTimeout))
+            var connectTask = _tcp.ConnectAsync(_config.IpAddress, _config.Port);
+            if (!connectTask.Wait((int)_config.ConnectTimeout.TotalMilliseconds))
+            {
+                try { _tcp.Close(); } catch { }
                 return false;
+            }
             _stream = _tcp.GetStream();
             return Login();
         }

Licensing/LicenseValidator.cs

@@ -29,7 +29,10 @@ namespace NcProgramManager.Licensing
                 using (var rsa = new RSACryptoServiceProvider())
                 {
                     rsa.FromXmlString(_publicKeyXml);
-                    return rsa.VerifyData(data, new SHA256CryptoServiceProvider(), signature);
+                    using (var sha256 = new SHA256CryptoServiceProvider())
+                    {
+                        return rsa.VerifyData(data, sha256, signature);
+                    }
                 }
             }
             catch

Licensing/MachineFingerprint.cs

@@ -13,7 +13,7 @@ namespace NcProgramManager.Licensing
             {
                 foreach (ManagementObject mo in moc)
                 {
-                    pcInfo = mo.Properties["processorID"].Value.ToString();
+                    pcInfo = mo.Properties["processorID"]?.Value?.ToString() ?? string.Empty;
                     break;
                 }
             }
@@ -23,7 +23,7 @@ namespace NcProgramManager.Licensing
             {
                 foreach (ManagementObject obj in searcher.Get())
                 {
-                    pcInfo += obj["SerialNumber"].ToString();
+                    pcInfo += obj["SerialNumber"]?.ToString() ?? string.Empty;
                     break;
                 }
             }