feat(container-config): add per-group model + effort overrides

Allow individual agent groups to opt into different models or effort levels
without changing host-wide defaults. Useful when one group is high-stakes
(opus, high effort) but most are routine (sonnet/haiku, low effort).

container.json gains two optional fields:
  - model: alias ("sonnet" | "opus" | "haiku") or full model ID
  - effort: "low" | "medium" | "high" | "xhigh" | "max"

Both omitted = SDK default (current behavior). The host plumbs them as
NANOCLAW_MODEL / NANOCLAW_EFFORT env vars at container spawn time; the
agent-runner reads them in providers/index.ts and threads through to the
provider via ProviderOptions. The Claude provider passes them straight to
sdkQuery options.

`effort` is currently typed as `any` because the @anthropic-ai/claude-
agent-sdk type doesn't surface it yet — passing it through still works at
runtime via the SDK's loose option handling. Drop the cast once the SDK
adds an `effort` field to its options type.

container/agent-runner/src/index.ts

@@ -91,6 +91,8 @@ async function main(): Promise<void> {
     mcpServers,
     env: { ...process.env },
     additionalDirectories: additionalDirectories.length > 0 ? additionalDirectories : undefined,
+    model: config.model,
+    effort: config.effort,
   });
 
   await runPollLoop({