fix(openai-agents): isolate config from generic OPENAI_* env vars

[dylanneve1]

Summary

• The openai-agents backend was silently overriding ~/.talon/config.json with OPENAI_API_KEY / OPENAI_BASE_URL / OPENAI_API_MODE from the shell. Operators who keep an OPENAI_API_KEY exported for unrelated tools were hitting 401s when pointing Talon at OpenRouter (their real OpenAI key was being sent to the wrong endpoint). Switched to a Talon-only env namespace — TALON_AGENTS_KEY, TALON_AGENTS_URL, TALON_AGENTS_API_MODE — that overrides config but doesn't shadow it via foreign vars.
• prompts/base.md hard-coded Claude Code tool names (Read, Write, Edit, Bash, Glob, Grep) as if every backend exposed them. With openai-agents selected those tools aren't registered, so models like DeepSeek v4 Flash would dutifully emit Read calls and @openai/agents would reject the run with Tool Read not found in agent Talon. Rewrote the prompt to instruct the model to use only the tools listed for the current run.

Env precedence (after this PR)

knob	precedence
key	TALON_AGENTS_KEY > config.openaiApiKey
baseURL	TALON_AGENTS_URL > config.openaiBaseUrl
apiMode	TALON_AGENTS_API_MODE > config.openaiApiMode

The underlying openai SDK still reads OPENAI_API_KEY for its own default client, but Talon always injects an explicit client whenever any key or baseURL is configured, so that fallback can no longer mask config.

Test plan

• npm run typecheck clean
• npm run lint (pre-existing warnings only)
• npx vitest run src/__tests__/openai-agents-*.test.ts — 36 tests pass, including new coverage that OPENAI_BASE_URL env is explicitly ignored when set alongside config
• Manual: OPENAI_API_KEY=sk-proj-… (real OpenAI key) exported in shell + openaiApiKey=sk-or-v1-… in ~/.talon/config.json → log line now reads key=config:openaiApiKey baseURL=config:openaiBaseUrl …, OpenRouter auth succeeds
• Manual: confirmed bot starts and stays up against deepseek/deepseek-v4-flash:free via OpenRouter

🤖 Generated with Claude Code

[claudiusthebot]

LGTM — approving. CI is 31/34 green; 3 Windows jobs still pending (slow infra, not related to the changes).

What's right here

src/backend/openai-agents/init.ts — The OPENAI_* → TALON_AGENTS_* namespace switch is the correct design. The problem it solves is real: anyone using Talon alongside other OpenAI tooling (a shell alias, a Claude Code session, a local dev environment) will have OPENAI_API_KEY exported, and pointing Talon at OpenRouter while that key is live would cause silent auth failures at the endpoint. The Talon-specific namespace makes intent explicit and prevents this whole class of confusion.

The source-tracking in the log line (key=config:openaiApiKey baseURL=env:TALON_AGENTS_URL) is a nice touch — it makes debugging auth issues much faster.

prompts/base.md — The original text hard-coded Read / Write / Edit / Bash / Glob / Grep as "the tools you have" regardless of backend. That was fine when Claude SDK was the only backend; with openai-agents it would cause models to emit Read(path="...") calls that the SDK immediately rejects with Tool Read not found. The rewrite ("use only the tools registered for this run") is backend-agnostic and will remain correct as more backends get added. Good fix that should have shipped with #199.

src/__tests__/openai-agents-models.test.ts — The explicit "OPENAI_BASE_URL env is ignored" test case is exactly right. A test that checks the absence of leakage is more valuable than one that just tests the happy path.

Minor note

The package-lock.json changes remove "peer": true from a handful of packages (grammy, hono, zod, express, etc.). These were probably marked peer in an earlier npm version's lockfile format and npm 10 re-normalized them on npm install. Harmless, but worth being aware of if you need to bisect a lockfile-related issue later.

Migration note (for the record)

With this PR, the OpenRouter migration config for June 1 is:

{
  "backend": "openai-agents",
  "model": "meta-llama/llama-3.3-70b-instruct",
  "openaiBaseUrl": "https://openrouter.ai/api/v1",
  "openaiApiKey": "<or-key>"
}

…or via env: TALON_AGENTS_KEY=sk-or-v1-… TALON_AGENTS_URL=https://openrouter.ai/api/v1. Clean and unsurprising.

Ready to land once the 3 Windows jobs clear.