feat(setup): quick onboarding, preserve .env vars, clean up boot logging (#821)

* feat(setup): quick onboarding, preserve .env vars, clean up boot logging (#751, #674)

- Add upsert_bootstrap_vars() to preserve user-added .env vars on re-onboarding
- Add --quick mode: auto-defaults DB + security, asks only LLM provider (2 steps)
- Auto-triggered onboarding uses quick mode for near-instant first run
- Fix NEAR AI model fetch to use cloud-api.near.ai when API key is set
- Handle missing WASM tools/channels directories gracefully
- Downgrade all boot/shutdown tracing::info! to debug (boot screen shows user output)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(setup): gate env_backend variable behind postgres feature flag [skip-regression-check]

Clippy lint fix — not a behavioral change, just moving a variable declaration
inside the cfg(feature = "postgres") block where it's used.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(review): address PR review comments

- WASM loaders: use tokio::fs::metadata, only treat NotFound as empty,
  propagate other IO errors, handle TOCTOU in read_dir
- bootstrap: only ignore NotFound in read_to_string, propagate other errors
- wizard: restore print_info/print_success for migrations in interactive
  mode (gated by !config.quick), keep tracing::debug for diagnostics
- tests: use shared crate::config::helpers::ENV_MUTEX instead of separate
  NEARAI_ENV_MUTEX to prevent cross-test env var races
- README: fix quick mode description to mention model selection, clarify
  auto_setup_database may prompt when DATABASE_URL is set

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat(setup): skip prompts for DATABASE_URL in quick mode [skip-regression-check]

auto_setup_database() now uses DATABASE_URL directly without calling
step_database_postgres() (which prompts for confirmation). Quick mode
should be fully non-interactive when env vars are already set.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(cli): update --quick help text to mention model selection [skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

src/config/embeddings.rs

@@ -100,13 +100,13 @@ impl EmbeddingsConfig {
         session: Arc<SessionManager>,
     ) -> Option<Arc<dyn EmbeddingProvider>> {
         if !self.enabled {
-            tracing::info!("Embeddings disabled (set EMBEDDING_ENABLED=true to enable)");
+            tracing::debug!("Embeddings disabled (set EMBEDDING_ENABLED=true to enable)");
             return None;
         }
 
         match self.provider.as_str() {
             "nearai" => {
-                tracing::info!(
+                tracing::debug!(
                     "Embeddings enabled via NEAR AI (model: {}, dim: {})",
                     self.model,
                     self.dimension,
@@ -117,7 +117,7 @@ impl EmbeddingsConfig {
                 ))
             }
             "ollama" => {
-                tracing::info!(
+                tracing::debug!(
                     "Embeddings enabled via Ollama (model: {}, url: {}, dim: {})",
                     self.model,
                     self.ollama_base_url,
@@ -130,7 +130,7 @@ impl EmbeddingsConfig {
             }
             _ => {
                 if let Some(api_key) = self.openai_api_key() {
-                    tracing::info!(
+                    tracing::debug!(
                         "Embeddings enabled via OpenAI (model: {}, dim: {})",
                         self.model,
                         self.dimension,