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---

.ciagent/CHECKPOINT.json

@@ -1,12 +1,12 @@
 {
-  "phase": 1,
+  "phase": 2,
   "stage": "complete",
   "milestone": "v1.22",
   "phase_role": "execution",
   "attempts": 0,
-  "updated_at": "2026-08-11T14:45:00Z",
+  "updated_at": "2026-08-11T14:50:00Z",
   "milestone_complete": false,
-  "tag": "v1.21.1",
-  "requirements": ["REQ-254","REQ-255","REQ-256"],
-  "notes": "v1.22 P1 complete. Tag v1.21.1. Theme CSS fixed (padding, overflow, image, title chrome). 23 slide tests pass. Proceeding to P2 (render scripts)."
+  "tag": "v1.21.2",
+  "requirements": ["REQ-257","REQ-258"],
+  "notes": "v1.22 P2 complete. Tag v1.21.2. render_deck.sh deleted, CLI versions pinned, 2x scale + transparent bg added. 4 render tests + 1 no-forge test pass. Proceeding to P3 (mermaid re-layout)."
 }