docs: re-anchor problem-statement clock to the fitted post-onset window

Dawn's delta review at 3292b35db caught the doc carrying two runways:
the problem statement still held kickoff's eyeballed ~3.5-4d doubling /
8-10d saturation, while the summary row read the fitted ~7d-to-80% —
and the eyeball figure was fitted across exactly the Jul-21-18:00Z
regime boundary the adjacent fit-window bullet forbids.

Problem statement now leads with the fitted post-onset clock (~3.4-3.5d
doubling, ~7d to 80%, r2=0.92) and demotes the kickoff figures to a
declared pre-onset eyeball. Same treatment for the ~150x/~400x family
growth (fitted: x9.6-12.4 over 9 days). G0's gate description (line
~595) keeps its original tasking text deliberately.

Model and configs untouched; doc only.

Co-authored-by: npub1qyvc0c5kl4gqv2fd97fsk46tu378sqgy35vc83rvgfwne90sel7s0ed67d <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@buzz.block.builderlab.xyz>
Signed-off-by: npub1qyvc0c5kl4gqv2fd97fsk46tu378sqgy35vc83rvgfwne90sel7s0ed67d <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@buzz.block.builderlab.xyz>

docs/redis-cluster-mode.md

@@ -74,11 +74,16 @@ disabled, auto-failover **enabled**, Multi-AZ **enabled** (verified via
 `describe-replication-groups` / `describe-cache-clusters`,
 profile `bb-public-operations-ro`).
 
-- `EngineCPUUtilization` (primary): 0.3% (Jul 21) → 8.4% (Jul 27) → 19.2%
-  (Jul 30) — doubling every ~3.5–4 days. Saturation in ~8–10 days if the
-  curve holds.
-- Driver is command volume: get/set/eval families each ~150x in two weeks,
-  pub/sub ~400x. Product growth (~80k users added), not a leak.
+- `EngineCPUUtilization` (primary): 0.3% (Jul 21) → 8.4% (Jul 27) → 19.5%
+  (Jul 30). **Fitted post-onset clock (P3, log-linear, r²=0.92): doubling
+  every ~3.4–3.5 days; ~7 days to 80%, ~8 to saturation.** (Kickoff's
+  eyeballed "~3.5–4 days / 8–10 days" spanned the pre-onset regime — see the
+  fit-window bullet below — and understated the urgency; the fitted number
+  is the citable one.)
+- Driver is command volume — product growth (~80k users added), not a leak.
+  Fitted 9-day post-onset growth is x9.6–12.4 across all command families
+  (kickoff's "~150x / ~400x in two weeks" were coarser eyeballs over a
+  window spanning the onset).
 - Whole-instance CPU ~4%, memory 0.09%, replication lag <1ms. Vertical
   scaling is dead: same-family bigger instances have identical single-core
   speed; r8g (Graviton4) buys ~25–30% single-thread ≈ 1.5 days at the current