Enable the decision model via EXPLORBOT_DECISION_MODEL / --decision-model

[DavertMik]

Summary

Config-free runs (prima, env-only explorbot) had no way to turn on the decision model (Jev): buildEnvConfig() never sets ai.decisionModel, and setting EXPLORBOT_AI_PROVIDER skips the global config entirely.

• EXPLORBOT_DECISION_MODEL, written as provider/model-id and split on the first slash (openrouter/typesafe/jev-1.13, typesafe/jev-latest). It is applied after config loading whatever the source (env-only, global, local), replaces provider/model and keeps tool/direct from the file. A value without a slash fails at startup. Registered in EXPLORBOT_ENV_VARS, so PRIMA_CLI_DECISION_MODEL works through prima's existing mirroring.
• --decision-model <model>: a shared BaseOption that sets the env var, registered on explorbot and prima-cli.
• Prima README: the recommended setup is now OpenRouter for everything (GPT-OSS 120B :nitro plus Jev), with env examples for Claude Code (settings.json), Codex (config.toml) and ~/.bashrc.
• Docs: env tables in agentic-usage.md / commands.md, a usage note in providers.md, CHANGELOG entry.

EXPLORBOT_DECISION_MODEL=openrouter/typesafe/jev-1.13 npx explorbot explore
npx prima-cli go "Settings" --decision-model typesafe/jev-latest

Notes

• The env tables were edited by hand: bunosh docs:sync doesn't run on main right now because the Bunoshfile fails to load (tests/regression/lib/assertions.ts has no status export). The rows match what the generator writes.

Test plan

• bun test tests/unit/config.test.ts boat/prima/tests/prima-env.test.ts: env var registry tests pass
• Env-only config with EXPLORBOT_DECISION_MODEL=openrouter/typesafe/jev-1.13 resolves to {"provider":"openrouter","model":"typesafe/jev-1.13"}
• A value without a slash fails with a clear error
• --decision-model sets the env var before a subcommand's action runs

🤖 Generated with Claude Code