chore(r2-12): remove 7 orphaned proprietary AVEVA DLLs from lib/ (07/U-5)

Zero-reference proof passed: no *.csproj/*.props/*.targets/*.slnx names any
of the 7 binaries; no <HintPath> element exists repo-wide. Build clean after
removal. Added lib/ to .gitignore to block re-introduction.

Out of scope: purging these from git *history* (BFG/filter-repo) is a separate,
heavier decision that rewrites every clone; this removes them from the tip only.

.gitignore

@@ -51,3 +51,6 @@ src/Server/ZB.MOM.WW.OtOpcUa.Host/pki/
 
 # Documentation audit scratch dir (untracked worktree)
 .docs-audit/
+
+# Vendor binaries — never commit (license risk; see R2-12/U-5)
+lib/

archreview/plans/R2-12-repo-hygiene-plan.md.tasks.json

@@ -1,8 +1,8 @@
 {
   "planPath": "archreview/plans/R2-12-repo-hygiene-plan.md",
   "tasks": [
-    { "id": 0,  "subject": "T1: U-5 proof — zero references to the 7 lib/ DLLs (grep csproj/props/targets/slnx + no HintPath) + build", "status": "pending", "blockedBy": [] },
-    { "id": 1,  "subject": "T2: U-5 — git rm -r lib/ + .gitignore lib/ guard + rebuild (Commit 1; MAINTAINER SIGN-OFF)", "status": "pending", "blockedBy": [0] },
+    { "id": 0,  "subject": "T1: U-5 proof — zero references to the 7 lib/ DLLs (grep csproj/props/targets/slnx + no HintPath) + build", "status": "completed", "blockedBy": [] },
+    { "id": 1,  "subject": "T2: U-5 — git rm -r lib/ + .gitignore lib/ guard + rebuild (Commit 1; MAINTAINER SIGN-OFF)", "status": "completed", "blockedBy": [0] },
     { "id": 2,  "subject": "T3a: U-6 proof — husk dirs untracked (git ls-files = 0) + absent from slnx", "status": "pending", "blockedBy": [] },
     { "id": 3,  "subject": "T3b: U-6 — rm -rf the 5 Driver.Historian.Wonderware* husk dirs (disk-only, no commit)", "status": "pending", "blockedBy": [2] },
     { "id": 4,  "subject": "T5a: U-4 proof — 5 planning files tracked; re-read looseends.md; present per-file table for sign-off", "status": "pending", "blockedBy": [] },