Introduces provider files (`data/claude-profile/providers/*.yaml`) that
bundle model ID, API base URL, API key source, and extra env vars. Phase 2.5
(provider selection) added between mode selection and launch, with a default
derived from the mode's driver field so existing Anthropic usage is unchanged.
Ships 5 providers: anthropic-haiku/sonnet/opus/opus-1m and minimax-sonnet.
MiniMax token decrypted from agent-runtimes SOPS env, stored at
~/.claude-secrets/minimax-auth-token. Adding new providers = one YAML file,
no script changes.
58 dryrun tests passing (up from 37).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
