agentic-sx Phase 2: branch — one branch = one agent (TDD)

space handle (repo + relations Datalog db); spawn! = branch-from-briefing
with a genesis spawn commit at the fork point; commit! verb snapshots a full
worktree VALUE into a typed agent-commit and CAS-advances the branch (no
shared index — multi-agent safe). Topology: fork-point via merge-base,
agents from refs, typed edges sub-agent-of/reviews/merges. Session merges
always record a two-parent session-merge commit (no-ff); conflicts commit
nothing and conclude via merge-resolve!. 53/53 (118/118 total).

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

lib/agentic/scoreboard.json

@@ -1,8 +1,9 @@
 {
   "suites": {
-    "schema": {"pass": 65, "fail": 0}
+    "schema": {"pass": 65, "fail": 0},
+    "branch": {"pass": 53, "fail": 0}
   },
-  "total_pass": 65,
+  "total_pass": 118,
   "total_fail": 0,
-  "total": 65
+  "total": 118
 }