structure-lint roster: decisions is a kind-only plane key (vanished door row is PLANE-ROOT-MISSING)

scripts/plane-keys.sh

@@ -58,7 +58,11 @@ PLANE_KEYS="llm a2a voice"
 # its plane-kind crate `crates/busbar-plane-<key>` (P3 DEL-MCP, ARCHITECT 2026-10-05: `mcp`). Never a
 # `crates/busbar-<key>` root; STILL a plane noun, so a needle gate that bans the other planes' keys
 # keeps banning it (`plane_noun_keys_other`). Leaving PLANE_KEYS must not let the word in.
-PLANE_KEYS_KIND_ONLY="mcp"
+# `decisions` (#48) never had a legacy-engine crate: one plane-kind crate, located by its door row
+# alone, so it is kind-only from birth and on this list so a vanished door row is PLANE-ROOT-MISSING
+# (xtask/src/planes.rs, the twin, pinned equal by xtask/tests/infra.rs). As a needle it reaches only
+# the report-only meters that source this list (plane-grep-gate.sh, plane-noun-gate.sh).
+PLANE_KEYS_KIND_ONLY="mcp decisions"
 
 # The protocol subset: every plane key except `llm`. Derived from PLANE_KEYS so adding a plane in
 # one place flows here automatically.

xtask/src/gates/structure_lint/selftest.rs

@@ -326,6 +326,32 @@ pub fn run<'a>(gate: &'a StructureLintGate, cx: &'a Ctx) -> Report<'a> {
         ),
     }
 
+    // THE FIFTH PLANE IS ON THE ROSTER TOO (#48). `decisions` is located by its door row alone and
+    // was on neither roster list, so taking the `plane-door` axis off `plane-decisions` dropped the
+    // plane from the roster with no finding. It is kind-only (`planes::PLANE_KEYS_KIND_ONLY`): the
+    // same plant must be PLANE-ROOT-MISSING naming it.
+    match cx.read(&manifest_rel) {
+        Ok(text) if text.contains("plane-decisions = \"plane-door\"") => {
+            let mut ov = Overlay::new();
+            ov.set(
+                &manifest_rel,
+                text.replace("plane-decisions = \"plane-door\"", "plane-decisions = \"\""),
+            );
+            report.push(tree_case(
+                cx,
+                gate,
+                "the decisions plane whose door row left the manifest is refused, not silently off the roster",
+                &[roots::ROW_PLANE_ROOTS],
+                ov,
+                &["PLANE-ROOT-MISSING", "decisions"],
+            ));
+        }
+        _ => report.note_infra_failure(
+            "structure-lint selftest: the manifest carries no `plane-decisions = \"plane-door\"` row, \
+             so the decisions plane-root case has nothing to plant against",
+        ),
+    }
+
     // A PLANE THE OLD CONSTANT NEVER NAMED (item 224). `PLANES` was `["mcp", "a2a"]`, so a second
     // home for voice could not be reported: the row "every plane resolves to exactly one home" was
     // true of the two planes it had been given. A second declaration of voice, in a directory named

xtask/src/planes.rs

@@ -46,7 +46,11 @@ pub const PLANE_KEYS: [&str; 3] = ["llm", "a2a", "voice"];
 /// `scripts/plane-keys.sh`'s `PLANE_KEYS_KIND_ONLY`. A roster that must notice a plane VANISHING
 /// (structure-lint's plane-roots row) reads these beside [`PLANE_KEYS`]: leaving the legacy roster
 /// must not take a plane off the roster that refuses an unlocatable plane.
-pub const PLANE_KEYS_KIND_ONLY: [&str; 1] = ["mcp"];
+///
+/// `decisions` (#48, the fifth plane) has never had a legacy-engine crate: it is one plane-kind
+/// crate, `busbar-plane-decisions`, located by its door row alone (`plane-decisions`, FLIP-DECISIONS).
+/// Off this list, a door row that vanished took it off structure-lint's roster with no finding.
+pub const PLANE_KEYS_KIND_ONLY: [&str; 2] = ["mcp", "decisions"];
 
 /// The default ownership grammar. Overridable for a fixture tree, the way
 /// `PLANE_ROOTS_GRAMMAR` is in the shell.