feat(cli): pic config --effective (masked secret resolution)

The §11 Phase-1 `config --effective` surface. Single-app today, "config"
= the app's secrets, so it cross-references the manifest's declared
secret names against what's set on the server and renders each masked:
`<set>` (managed / on-server-not-in-manifest) or `<unset>` (declared but
not pushed). Values are never fetched or shown (§4.6). Shaped to grow an
`--explain` mode and inherited `vars` when groups/vars arrive (Phase 3).

Tested: a journey verifying declared-but-unset → `<unset>`, post-`secret
set` → `<set>`/managed, and the value never appears in output.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud-cli/tests/cli.rs

@@ -18,6 +18,7 @@ mod api_keys;
 mod apply;
 mod apps;
 mod auth;
+mod config;
 mod dead_letters;
 mod email_queue;
 mod enabled;

crates/picloud-cli/tests/config.rs

@@ -0,0 +1,57 @@
+//! `pic config --effective` — masked secret resolution against the manifest.
+
+use std::fs;
+
+use predicates::prelude::*;
+use tempfile::TempDir;
+
+use crate::common;
+use crate::common::cleanup::AppGuard;
+
+#[ignore = "needs DATABASE_URL pointing at a running Postgres"]
+#[test]
+fn config_effective_masks_and_classifies_secrets() {
+    let Some(fx) = common::fixture_or_skip() else {
+        return;
+    };
+    let env = common::admin_env(fx);
+    let slug = common::unique_slug("config");
+    common::pic_as(&env)
+        .args(["apps", "create", &slug])
+        .assert()
+        .success();
+    let _guard = AppGuard::new(&env.url, &env.token, &slug);
+
+    let dir = TempDir::new().unwrap();
+    let manifest_path = dir.path().join("picloud.toml");
+    fs::write(
+        &manifest_path,
+        format!("[app]\nslug = \"{slug}\"\nname = \"Cfg\"\n\n[secrets]\nnames = [\"API_KEY\"]\n"),
+    )
+    .unwrap();
+
+    // Declared but not pushed → masked + flagged unset; value never shown.
+    common::pic_as(&env)
+        .args(["config", "--effective", "--file"])
+        .arg(&manifest_path)
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("API_KEY"))
+        .stdout(predicate::str::contains("<unset>"))
+        .stdout(predicate::str::contains("not pushed"));
+
+    // Push it → now masked as <set> / managed, still never the value.
+    common::pic_as(&env)
+        .args(["secrets", "set", "--app", &slug, "API_KEY"])
+        .write_stdin("super-secret-value")
+        .assert()
+        .success();
+    common::pic_as(&env)
+        .args(["config", "--effective", "--file"])
+        .arg(&manifest_path)
+        .assert()
+        .success()
+        .stdout(predicate::str::contains("<set>"))
+        .stdout(predicate::str::contains("managed"))
+        .stdout(predicate::str::contains("super-secret-value").not());
+}