feat(project-tool): per-env approval-policy gating (§4.2/§6)

Salvaged from the superseded feat/hierarchies-extension-points branch (M5),
re-ported onto main's evolved tree-apply engine. Fills the §7/§11.1 "per-env
approval-policy gating" that main's design doc still lists as intended but
unbuilt.

A project's root manifest declares which environments require explicit
approval; `pic apply --dir --env <e>` to a confirm-required env needs an
explicit `--approve <e>` (a blanket `--yes` does NOT cover it). The approval
is admin-gated (admin on every declared node) and audited, and the policy
folds into the bound-plan token.

- manifest: `[project]` block → ManifestProject { environments[{name,confirm}] },
  root-manifest-only (rejected elsewhere by build_tree).
- discover: build_tree emits `project` into the bundle from the root manifest.
- apply_service: TreeBundle.project + ProjectPolicy; policy folds into the
  state_token; plan surfaces approvals_required; ApplyError::ApprovalRequired
  → 409.
- apply_api: enforce_env_approval (after authz_tree) — refuses a gated env not
  in approved_envs, requires AppAdmin/GroupAdmin on every declared node on
  approval, audits. Server re-derives policy from the bundle (authoritative).
- CLI: --approve (repeatable); resolve_approvals refuses a gated env
  non-interactively, prompts on a TTY; plan renders gated envs. Single-node
  apply --file refuses a confirm-required env and directs to --dir.
- approval journey + manifest/ProjectPolicy unit tests. No migration (policy
  lives in the manifest, like takeover/blast-radius).

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

crates/picloud-cli/src/discover.rs

@@ -45,10 +45,15 @@ fn walk(dir: &Path, out: &mut Vec<PathBuf>) -> Result<()> {
     Ok(())
 }
 
-/// Build the wire tree bundle (`{ nodes: [{kind, slug, bundle}] }`) from every
-/// manifest under `root`. Returns the JSON plus the node count. Rejects a tree
-/// that names the same (kind, slug) twice.
-pub fn build_tree(root: &Path, env: Option<&str>) -> Result<(Value, usize)> {
+/// Build the wire tree bundle (`{ nodes: [{kind, slug, bundle}], project }`)
+/// from every manifest under `root`. Returns the JSON, the node count, and the
+/// root manifest's `[project]` environment policy (M5, empty if none). Rejects a
+/// tree that names the same (kind, slug) twice, or declares `[project]` anywhere
+/// but the root manifest.
+pub fn build_tree(
+    root: &Path,
+    env: Option<&str>,
+) -> Result<(Value, usize, Vec<crate::manifest::ManifestEnvironment>)> {
     let paths = find_manifests(root)?;
     if paths.is_empty() {
         bail!(
@@ -56,11 +61,25 @@ pub fn build_tree(root: &Path, env: Option<&str>) -> Result<(Value, usize)> {
             root.display()
         );
     }
+    let root_manifest = root.join(MANIFEST_FILE);
     let mut nodes = Vec::with_capacity(paths.len());
     let mut seen: HashSet<(String, String)> = HashSet::new();
+    let mut project: Option<crate::manifest::ManifestProject> = None;
     for path in &paths {
         let manifest = Manifest::load_with_env(path, env)
             .with_context(|| format!("loading {}", path.display()))?;
+        // `[project]` is project-level — valid only on the tree's root manifest.
+        if let Some(p) = &manifest.project {
+            if path == &root_manifest {
+                project = Some(p.clone());
+            } else {
+                bail!(
+                    "{} declares [project], which is only valid on the root manifest ({})",
+                    path.display(),
+                    root_manifest.display()
+                );
+            }
+        }
         let base_dir = path.parent().unwrap_or_else(|| Path::new("."));
         let bundle = build_bundle(&manifest, base_dir)?;
         let kind = if manifest.is_group() { "group" } else { "app" };
@@ -71,5 +90,20 @@ pub fn build_tree(root: &Path, env: Option<&str>) -> Result<(Value, usize)> {
         nodes.push(json!({ "kind": kind, "slug": slug, "bundle": bundle }));
     }
     let count = nodes.len();
-    Ok((json!({ "nodes": nodes }), count))
+    let envs = project
+        .as_ref()
+        .map(|p| p.environments.clone())
+        .unwrap_or_default();
+    let mut bundle = json!({ "nodes": nodes });
+    if let Some(p) = &project {
+        bundle.as_object_mut().expect("json object").insert(
+            "project".into(),
+            json!({
+                "environments": p.environments.iter()
+                    .map(|e| json!({ "name": e.name, "confirm": e.confirm }))
+                    .collect::<Vec<_>>(),
+            }),
+        );
+    }
+    Ok((bundle, count, envs))
 }