docs(turn-loop): split into index + claude-invocation/config/mcp sub-pages, condense the loop

CLAUDE.md

@@ -86,7 +86,10 @@ read them à la carte.
 - **"How does the per-agent terminal classify + colour
   events?"** → [`docs/terminal-rendering.md`](docs/terminal-rendering.md).
 - **"How does claude get its prompt and what tools does it have?"** →
-  [`docs/turn-loop.md`](docs/turn-loop.md).
+  [`docs/turn-loop.md`](docs/turn-loop.md) (index: the loop, binary shape,
+  turn outcomes; sub-pages:
+  [`claude-invocation`](docs/turn-loop/claude-invocation.md),
+  [`config`](docs/turn-loop/config.md), [`mcp`](docs/turn-loop/mcp.md)).
 - **"How do config changes flow from manager to operator to
   container?"** → [`docs/approvals.md`](docs/approvals.md).
 - **"What state survives destroy / purge / restart?"** →