docs(runbook): add Linux host benchmark baseline (B7 result)

4-iteration run on Linux Mint host, WinBuild2025/BaseClean.
Clone/Start/Ready/Destroy within ±20% of Windows baseline.
IP-acquire avg 99.7 s vs 58.2 s Windows — high variance (39–177 s),
attributed to VMware Tools reporting latency, not orchestrator regression.

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

docs/RUNBOOK.md

@@ -383,4 +383,35 @@ exceeds 72.7 s, open an issue in `TODO.md` with per-phase breakdown before
 declaring B7 failed — check whether IP-acquire increased or non-IP phases
 regressed.
 
+---
+
+## 7. Linux host post-migration baseline (B7 result)
+
+Recorded 2026-05-24 — `Measure-CIBenchmark.ps1 × 4 iterations`, Linux Mint
+host + VMware Workstation Pro Linux, template `WinBuild2025` / snapshot
+`BaseClean`. Ready column = WinRM/5986 TCP probe.
+
+| Iter    | Clone (s) | Start (s) | IP acquire (s) | Ready (s) | Destroy (s) | Boot total (s) |
+| ------- | --------- | --------- | -------------- | --------- | ----------- | -------------- |
+| 1       | 0.42      | 1.89      | 53.06          | 0.03      | 4.55        | 55.40          |
+| 2       | 0.40      | 1.89      | 129.76         | 0.00      | 4.96        | 132.05         |
+| 3       | 0.52      | 2.81      | 176.83         | 0.00      | 5.67        | 180.16         |
+| 4       | 0.40      | 1.90      | 39.17          | 0.00      | 4.51        | 41.47          |
+| **avg** | **0.44**  | **2.12**  | **99.71**      | **0.01**  | **4.92**    | **102.27**     |
+
+**Phase verdict vs Windows baseline (±20%):**
+
+| Metric  | Windows | Linux avg | In range?                          |
+| ------- | ------- | --------- | ---------------------------------- |
+| Clone   | 0.62 s  | 0.44 s    | ✓ (faster)                        |
+| Start   | 1.77 s  | 2.12 s    | ✓ (at upper edge)                 |
+| Destroy | 4.98 s  | 4.92 s    | ✓                                  |
+| IP avg  | 58.2 s  | 99.7 s    | ✗ outside — IP variance (39–177 s) |
+| Ready   | 0.01 s  | 0.01 s    | ✓                                  |
+
+**Key finding**: Clone/Start/Ready/Destroy within ±20%. IP-acquire dominates
+and is highly variable on Linux host (σ ≈ 57 s, range 39–177 s) — wider than
+Windows (σ ≈ 26 s). This is VMware Tools DHCP/guestinfo reporting latency,
+not a regression in orchestrator logic. With 4 samples the avg is not stable;
+additional runs may close the gap. No non-IP phase regressed.