fix(P4): trim/split 8 overflowing slides + remove header (REQ-261)

Split slide 3 (Objectives + Anti-Goals) into Slide 3 (Objectives)
+ Slide 4 (Anti-Goals). Split slide 8 (Attestation Matrix) into
Slide 9 (QA concerns, 3 rows) + Slide 10 (Prod/DR concerns, 7 rows).
Main slide count 18 -> 20.

Trimmed: slide 7 (Pipeline) reduced to 3 bullets (4th covered by
diagram). slide 11 (Telemetry) reduced to 3 bullets. slide 14
(Deferred) merged 3 Live-AWS rows into 1 (8 -> 6 rows). slide 17
(Quarter-by-Quarter) dropped Grounding column (5 -> 4 cols). Global
table cell padding reduced (6px 10px -> 4px 8px) so 8-13 row tables
fit.

Removed header: from frontmatter (keep footer: + paginate only).
The full 51-char deck title in BOTH header and footer was redundant
chrome eating ~35px on every slide.

Updated test_marp_deck_slide_count (18 -> 20 main + 1 appendix).
Updated README slide-count convention (18 -> 20).

---ci---
project: acdl
phase: 4
milestone: v1.22
status: execute
phase_role: execution
---/ci---

tests/test_slides_pipeline.py

@@ -202,7 +202,9 @@ def test_marp_deck_title_is_autonomous_cloud_delivery():
 
 
 def test_marp_deck_slide_count():
-    """REQ-245: 18 main slides + 1 appendix = 19 slides total."""
+    """REQ-245/261: 20 main slides + 1 appendix = 21 slides total.
+    v1.22 split slides 3 (Objectives+Anti-Goals) and 8 (Attestation
+    Matrix) to relieve overflow, increasing the count from 18 to 20."""
     text = MARP_DECK.read_text()
     # Count slide separators: each slide ends with --- (except the last)
     # The frontmatter is one --- ... --- block, then each slide is separated by ---
@@ -210,8 +212,8 @@ def test_marp_deck_slide_count():
     slide_headings = re.findall(r"^## (?:Slide|Appendix) ", text, re.MULTILINE)
     main_slides = re.findall(r"^## Slide ", text, re.MULTILINE)
     appendix_slides = re.findall(r"^## Appendix ", text, re.MULTILINE)
-    assert len(main_slides) == 18, \
-        f"expected 18 main slides, found {len(main_slides)}: {slide_headings}"
+    assert len(main_slides) == 20, \
+        f"expected 20 main slides, found {len(main_slides)}: {slide_headings}"
     assert len(appendix_slides) == 1, \
         f"expected 1 appendix slide, found {len(appendix_slides)}"