docs(examples): codebase-qa demo — watch the governor kill a runaway agent

[prashar32]

Adds examples/codebase-qa/, a self-contained, runnable demo that shows the headline feature end to end: deterministic budget/loop governance halting a runaway agent, with a real model.

What it is

A plain ReAct-style codebase Q&A agent (no RAG, no vector DB, no framework) built on the Python SDK. Every model call is routed through run.proxy_config(), so the proxy meters tokens/cost and the governor enforces the per-run loop / dollar / time budget around the loop. The kill comes from the daemon (HTTP 402), surfaced as BudgetExceeded — never faked in the script.

Two modes:

• --mode normal — a sensible question that completes within budget; prints each step, tokens, and running USD cost, then the answer.
• --mode runaway — the same agent with a deliberately weak stopping condition (told to re-read every file), so it loops. Counters climb, then the loop budget halts it cleanly.

Layout

examples/codebase-qa/
├── agent.py            # the governed ReAct agent (stdlib + RiskKernel SDK only)
├── requirements.txt    # the RiskKernel SDK (stdlib-only itself)
├── README.md           # 60-second run for both modes + expected output
└── sample/             # a tiny todo app used as the target codebase
    ├── main.py  store.py  models.py  config.py  README.md

Dependencies

None beyond the RiskKernel Python SDK and an LLM provider key (BYO ANTHROPIC_API_KEY on the daemon). The proxy call uses stdlib urllib.

Notes

• Read-only agent, so it doesn't exercise the approval gate; the README points to governed_tool / run.approve for the side-effecting case.
• Also wired into the root README and CHANGELOG ([Unreleased]).