fix(cli): env-aware config, pull clobber guard, strict overlays, 409 hint

Four review fixes on the `pic` surface:

- `config --effective` gains `--env`: it now resolves through the same
  overlay as `plan`/`apply`, so the masked report targets the app those
  commands act on instead of silently reading the base slug's secrets.
- `pull` gains `--force` and refuses to overwrite an existing
  `picloud.toml` (and colliding `scripts/*.rhai`) without it — fail-fast
  before any network call or write, mirroring `init`.
- Overlays (`ManifestOverlay`/`OverlayApp`) get `deny_unknown_fields`: a
  `[[scripts]]`/`[[routes]]`/`[[triggers]]` table or a typo'd key in an
  overlay now errors loudly instead of being silently dropped. +unit test.
- `apply` 409 (StateMoved — the only 409 the endpoint emits) surfaces an
  actionable hint (re-run `pic plan`, or `--force`) instead of a bare
  `HTTP 409`.

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

crates/picloud-cli/src/manifest.rs

@@ -112,7 +112,13 @@ fn overlay_path(base_path: &Path, env: &str) -> std::path::PathBuf {
 
 /// A sparse per-environment overlay (`picloud.<env>.toml`). Only the fields
 /// that vary per environment today — slug/name and secret names.
+///
+/// `deny_unknown_fields`: an overlay can carry *only* `[app]` and `[secrets]`.
+/// Scripts/routes/triggers belong in the shared base manifest, so a
+/// `[[scripts]]`/`[[routes]]`/`[[triggers]]` table (or a typo'd key) in an
+/// overlay is a mistake — error loudly rather than silently dropping it.
 #[derive(Debug, Clone, Default, Deserialize)]
+#[serde(deny_unknown_fields)]
 pub struct ManifestOverlay {
     #[serde(default)]
     pub app: OverlayApp,
@@ -121,6 +127,7 @@ pub struct ManifestOverlay {
 }
 
 #[derive(Debug, Clone, Default, Deserialize)]
+#[serde(deny_unknown_fields)]
 pub struct OverlayApp {
     #[serde(default)]
     pub slug: Option<String>,
@@ -461,6 +468,26 @@ mod tests {
         assert_eq!(m.scripts.len(), 2);
     }
 
+    #[test]
+    fn overlay_rejects_non_overlay_tables() {
+        // An overlay carries only [app]/[secrets]. Scripts/routes/triggers
+        // belong in the shared base, so a `[[scripts]]` table (or a typo'd
+        // key) in an overlay must error loudly, not be silently dropped.
+        let err = toml::from_str::<ManifestOverlay>(
+            "[app]\nslug = \"blog-staging\"\n\n\
+             [[scripts]]\nname = \"hello\"\nfile = \"scripts/hello.rhai\"\n",
+        )
+        .expect_err("overlay with [[scripts]] must be rejected");
+        assert!(
+            err.to_string().contains("scripts") || err.to_string().contains("unknown"),
+            "error should point at the offending table: {err}"
+        );
+
+        // Typo'd key inside [app] is likewise rejected.
+        toml::from_str::<ManifestOverlay>("[app]\nslag = \"oops\"\n")
+            .expect_err("overlay with a typo'd [app] key must be rejected");
+    }
+
     #[test]
     fn overlay_path_derivation() {
         assert_eq!(