chore(codex): add controlled Spark agents

AGENTS.md

@@ -20,3 +20,20 @@ Canonical source limits:
 
 Every component change must update its registry entry and the living catalog. Preserve keyboard behavior, portal layering and theme independence.
 
+## Controlled subagent orchestration
+
+All subagent work in this repository follows
+`docs/CODEX_SUBAGENT_GOVERNANCE.md`.
+
+- The primary Sol agent owns requirements, architecture, integration, final
+  verification, commits, pushes, deployments and user communication.
+- Use `spark_explorer` only for bounded read-only evidence gathering.
+- Use `spark_worker` only for small edits with an exact path allowlist and explicit
+  verification commands.
+- Announce every agent, model, task, access mode and allowed scope before spawning
+  it. Report every completion, interruption and escalation to the user.
+- Run at most two subagents concurrently and at most one write-capable agent.
+- Subagents must not spawn other agents, mutate external systems, commit, push,
+  deploy, install dependencies or expand their own scope.
+- Do not invent per-agent token measurements. Report measured usage only when the
+  product exposes it; otherwise report model, task, state, turns and outcome.