fix(P3): re-layout mermaid diagrams to TB + re-render 2x transparent (REQ-259,260)

REQ-259: telemetry-live-ops.mmd kept as flowchart TB (the 3-way
branch C/D/E makes LR too wide at 4.22 aspect; TB gives 0.63 which
is legible at h:480). Re-rendered at 2x transparent (1024x1628).
Marp deck directive updated: ![w:900] -> ![h:480] so the image
renders at a legible height using the img.tall class budget.
REQ-260: platform-pipeline.mmd restructured from 10-node LR chain
(aspect 13.52, illegible 1000x74 strip) to 4-node TB with combined
nodes (Contract->Resolver->Adapter, Wiz->Confidence->Stage gate,
Apply->Evidence). Re-rendered at 2x transparent (552x1116, aspect
0.49). Marp deck directive: ![w:1000] -> ![h:480].

Aspect-ratio bounds revised from [1.2, 2.5] to [0.4, 4.0] (GRILL
revision 1 scoped the test to deck-referenced PNGs only; the bounds
are widened to accept tall diagrams that use img.tall class). The
bounds still catch the original extreme outliers (13.52x and 0.22x).

---ci---
project: acdl
phase: 3
milestone: v1.22
status: execute
phase_role: execution
---/ci---

docs/presentations/nova-autonomous-cloud-delivery-marp.md

@@ -102,7 +102,7 @@ Every hour a developer spends writing, deploying, fixing, or remediating infrast
 
 **How intent becomes verified infrastructure — fail-fast policy scanning before the plan, runtime scanning after it.**
 
-![w:1000](assets/png/platform-pipeline.png)
+![h:480](assets/png/platform-pipeline.png)
 
 - **Contract → resolver → adapter → Checkov on static code (before plan) → terraform plan → Wiz on the plan → confidence signal → stage gate → apply → evidence + ledger**
 - **Fail-fast, quick feedback** — Checkov runs on the authored Terraform code before `terraform plan` so developers get immediate policy feedback
@@ -152,7 +152,7 @@ Separation-of-duties on prod: the approver cannot be the same person who built t
 
 **Every metric in this deck is traceable to a real emitted signal — the live-ops dashboard makes operations visible in PowerBI.**
 
-![w:900](assets/png/telemetry-live-ops.png)
+![h:480](assets/png/telemetry-live-ops.png)
 
 - **Platform components → CloudEvents envelope → event log + decision ledger + run records → collector → cold store → PowerBI views → live ops dashboard**
 - **The live ops dashboard (PowerBI)** surfaces the four CTO-grade metrics (Lead Time, Vulnerability Count, MTTR, Cloud Spend) alongside trust metrics (Decision Ledger coverage, Attestation coverage) and efficiency metrics (touchless resolution, escalation frequency)