plans/sx-review: sx-commit START — fix work begins from 8651cefe

Adds a starting-point decision-commit on the coordinator branch
(sx1:9f05cceb...) marking the state where all review infrastructure is in
place — plan, rulings, quick-wins batch (dc7aa709), and the forge itself —
as the baseline from which the fix program starts. Records the sequencing
rule (W14 test-gate first, then W1/K01) so the next agent picks up correctly.

Coordinator branch: spawn -> baseline -> done -> START (4 commits).
forge.sxdata re-dumped (46KB); forge-build.sxsrc stays the reproducible source.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plans/sx-review/forge-build.sxsrc

@@ -95,11 +95,19 @@
       "(batch :commit \"dc7aa709\" :fixed (K02 K09 K11 K18 K20 K39 K49 K73 K105 C1 C1b S4 F13) :partial (K19 K42 C24 F14) :suite \"5762p-274f-baseline\")")
     {:message "quick-wins batch dc7aa709 recorded"}))
 
+; STARTING POINT — all review infrastructure is in place (plan, rulings,
+; quick-wins batch, forge); fixing begins from this real-git state.
+(define fb-start
+  (agentic/commit! fb-sp "coordinator" "decision"
+    (assoc {} "START.sx"
+      "(starting-point :real-git \"8651cefe\" :tree \"plan+rulings+forge+quick-wins\" :suite \"5762p-274f-baseline\" :next \"W14 test-gate first, then W1 K01 guard-hang\" :rule \"no semantic fix before its pinning test + gate\")")
+    {:message "START — fix work begins from 8651cefe; W14 gate first, then W1/K01"}))
+
 ; --- durable dump: kv + streams of the shared backend, serialized ---
 (define fb-forge-serialize
   (fn ()
     (sx-serialize
-      {:review "sx-review" :baseline fb-baseline :done fb-done
+      {:review "sx-review" :baseline fb-baseline :done fb-done :start fb-start
        :agents (agentic/agents fb-sp)
        :workstream-cids fb-ws-cids
        :kv (map (fn (k) (list k ((get fb-db :kv-get) k))) ((get fb-db :kv-keys)))