docs(review): P1 fixes — sync slide-count metadata + README directory layout

Review of P71 (v1.13) flagged 2 P1 documentation-metadata drift items:
1. Source .md length headers undercounted by 1 (excluded Appendix TOC slide)
2. README.md drifted — missing 12 new asset files + stale slide/section counts

Fixes:
- how-the-platform-works.md: 18 -> 19 slides (10 main + TOC + 8 appendix)
- the-developer-experience.md: 17 -> 18 slides (10 main + TOC + 7 appendix)
- both *-talking-points.md companion headers updated to match
- README.md directory layout: added 6 new .mmd + 6 new .png files
- README.md appendix convention: "10 main + 6 appendix (17 total)" ->
  per-deck counts (A1-A8 platform, A1-A7 developer, both with TOC)
- README.md current-decks table: slide counts updated to 19/18
- README.md talking-points structure: "10 main + 7 appendix" -> TOC-aware

No factual/capability claim changes. 16 docs tests pass.

---ci---
project: acdl
phase: 71
milestone: v1.13
status: verify
lessons:
  - P1 fix: sync slide-count metadata across source .md, talking-points, README
---/ci---

docs/presentations/the-developer-experience-talking-points.md

@@ -1,6 +1,6 @@
 # The Developer Experience — Talking Points
 
-> **Companion to:** `the-developer-experience-marp.md` (10 main + 7 appendix = 17 slides)
+> **Companion to:** `the-developer-experience-marp.md` (10 main + Appendix TOC + 7 appendix = 18 slides)
 > **Content source:** `the-developer-experience.md` (full source of truth with speaker notes)
 > **Purpose:** Presenter-ready cues — 3-6 talking points per slide + the one key takeaway the audience should remember.
 > **Audience:** Senior Leadership — CTO, Head of Cloud, Head of Infrastructure, Head of DevOps