feat(logging): honor OpenCode's host logLevel + configurable level for standalone runtime

[stephane-segning]

Summary

• Inside OpenCode, the plugin now reads the host's top-level config.logLevel ("DEBUG" | "INFO" | "WARN" | "ERROR") so a single host-level setting drives both the console output and the forwarded client.app.log records — no separate plugin knob to keep in sync.
• Standalone consumers of OAuth2ModelSyncPlugin (anyone using the runtime without the OpenCode shell) can pass logLevel via OAuth2ModelSyncConfigInput; values are validated against "debug" | "info" | "warn" | "error" and default to "info".
• The OpenCode logger gates by a live level reference, so the threshold from the config hook takes effect on the very first emitted record.

Why

Previous behavior hardcoded "info", so debug-level OAuth/discovery traces were invisible even when the host CLI was in debug mode. The first iteration added a dedicated pluginConfig.oauth2ModelSync.logLevel knob — but that meant two log-level settings that could disagree, and a confusing UX where bumping OpenCode's own level didn't reach the plugin. Deferring to the host's config.logLevel resolves both problems while keeping a standalone-friendly escape hatch.

Notes for reviewers

• fromOpenCodeLogLevel is intentionally permissive: it returns undefined (rather than throwing) on unknown values so the host owns validation of its own field. The plugin then falls back to DEFAULT_LOG_LEVEL ("info").
• createOpenCodeLogger now bypasses createJsonConsoleLogger's internal filter and gates through a getMinLevel() closure so level changes from the config hook apply immediately, including the first call.
• README updated: the new behavior is documented as a note under the pluginConfig.oauth2ModelSync table rather than as a separate field row.

Test plan

• pnpm --filter @vymalo/opencode-oauth2 typecheck — clean
• pnpm --filter @vymalo/opencode-oauth2 test — 101 passed (7 new: 3 covering standalone logLevel validation, 1 OpenCode-host-logLevel smoke test, 3 fromOpenCodeLogLevel unit tests)
• biome check on touched files — clean
• Manual smoke: set logLevel: "DEBUG" in opencode.json, run a sync, confirm oauth_* debug events appear

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request integrates the host's top-level logLevel configuration into the opencode-oauth2 plugin, ensuring that plugin logs honor the host's log level settings. Feedback on these changes highlights two main improvements: first, updating the currentLogLevel before calling collectManagedProviders so that initial configuration parsing logs are filtered correctly; and second, exporting and reusing the LOG_LEVEL_PRIORITY map from logging.ts instead of duplicating it in opencode.ts to maintain a single source of truth.