fix(project-tool): close M5+M3 review findings (authz + data-loss + None-path)

A fresh two-lens end-to-end review (security + correctness) of the committed
M5/M3 diff surfaced four real defects; all fixed here with regressions.

- HIGH (M5 authz bypass) — `enforce_env_approval` resolved a group node with a
  bare `get_by_slug` and SKIPPED the GroupAdmin gate on miss. A node addressed
  by the group's UUID (which the apply still resolves) let a group EDITOR apply
  to a confirm-required env without admin. Now resolves UUID-or-slug and fails
  closed, mirroring authz_tree / prepare_tree. Raw-wire regression added.

- FIX-FIRST (M3 correctness) — the legacy `project_key=None` path was not inert:
  the conflict loop pushed a conflict for any owned group (`Some(oid) != None`),
  so a keyless/direct-API tree apply touching an already-claimed group was
  spuriously 409'd. Ownership classification is now gated on a key being present
  (the discriminator is key-present, not project-persisted, so a first-ever
  keyed apply still sees an already-owned group as a conflict). Regression added.

- FIX-FIRST (M3 data-loss) — the structural-prune guard checked collection
  MARKERS (`group_collections`) but data outlives its marker: un-declaring a
  `collections=[...]` entry drops the marker while the kv/docs/files/queue rows
  survive until group delete. A dropped-then-pruned group would silently CASCADE
  that orphaned data. The guard now EXISTS-checks the actual data tables
  (group_kv_entries/docs/files/queue_messages) plus secrets + markers.

- MEDIUM (audit) — group ownership takeover (and claim) now emit a
  tracing::info! audit line with the actor + ousted owner, matching the M5
  gated-env audit. Previously only a report counter.

Also: documented WHY `pic plan --dir` mints the project key (a rare write for a
read-only command) — plan and apply must present the same key or the ownership
token folds diverge and trip a spurious StateMoved.

Re-verified: 411 manager-core lib tests; 28 CLI journeys (incl. 2 new
regressions: uuid-slug admin gate, keyless legacy apply); workspace clippy
-D warnings + fmt clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/picloud-cli/tests/ownership.rs

@@ -286,3 +286,47 @@ fn prune_refuses_to_cascade_a_groups_shared_data() {
         "a group owning shared collections must NOT be pruned"
     );
 }
+
+#[ignore = "needs DATABASE_URL pointing at a running Postgres"]
+#[test]
+fn legacy_apply_without_project_key_ignores_ownership() {
+    // Regression (§7): a tree apply with NO project key (legacy / direct-API
+    // caller) must skip ALL ownership — no conflicts, no claims. A bug gated the
+    // conflict classification on `our_project_id` (None for a keyless caller),
+    // so ANY already-owned declared group was spuriously rejected. Drive the raw
+    // wire without `project_key` (the CLI always sends one).
+    let Some(fx) = common::fixture_or_skip() else {
+        return;
+    };
+    let env = common::admin_env(fx);
+    let slug = common::unique_slug("own-legacy");
+    let _g = GroupGuard::new(&env.url, &env.token, &slug);
+    create_group(&env, &slug, None);
+
+    // Repo A claims the group (a normal CLI apply — sends a project key).
+    let repo_a = group_dir(&slug, "");
+    assert!(
+        apply(&env, repo_a.path(), &[]).status.success(),
+        "claim apply should succeed"
+    );
+
+    // A keyless raw apply of the same (now-owned) group must NOT 409 — ownership
+    // is simply not evaluated without a project key.
+    let http = reqwest::blocking::Client::new();
+    let body = serde_json::json!({
+        "bundle": { "nodes": [{ "kind": "group", "slug": slug, "bundle": {} }] },
+        "prune": false,
+    });
+    let resp = http
+        .post(format!("{}/api/v1/admin/tree/apply", env.url))
+        .bearer_auth(&env.token)
+        .json(&body)
+        .send()
+        .expect("tree apply");
+    assert!(
+        resp.status().is_success(),
+        "a keyless (legacy) apply must ignore ownership, not conflict (got {}: {})",
+        resp.status(),
+        resp.text().unwrap_or_default()
+    );
+}