fix: drop the trigger word for an Agent that cannot read the Skill

src/core/registry.mjs

@@ -481,8 +481,14 @@ export function buildRegistry(customHome = null) {
         Object.entries(agentDirs)
           .filter(([agentKey, cfg]) => isAgentVisible(cfg, agentKey, overrides))
           // An Agent that cannot read the Skill has no trigger word for it.
-          // Listing one told the user to type a command that does nothing.
-          .filter(([agentKey]) => !agentOnly || agentKey === agentOnly)
+          // Listing one tells the user to type a command that does nothing.
+          //
+          // `agents` above already answers "can this Agent read it": the link
+          // exists, or the Agent scans the SSOT natively. Asking that map is
+          // what makes this true after an unlink or a trash restore too — both
+          // leave the Skill in place with its links gone, and both used to keep
+          // advertising the trigger word for Agents that had just lost it.
+          .filter(([agentKey]) => agents[agentKey])
           .map(([agentKey, cfg]) => [
             agentKey,
             `${cfg.triggerPrefix || "/"}${cfg.type === "native" ? fmName || name : name}`,

test/registry.test.mjs

@@ -93,6 +93,12 @@ test("registry uses configured agent triggers and metadata overrides", (t) => {
   writeFileSync(join(skillDir, "SKILL.md"), "---\nname: demo\ndescription: demo skill\n---\n");
   // cursor is switched on explicitly; gemini is left to the default, and its
   // directory does not exist in this sandbox.
+  // The link has to exist for cursor to have a trigger word at all: a trigger
+  // is what an Agent that can reach the Skill would answer to, and cursor can
+  // only reach it through this link.
+  const cursorSkills = join(tmp, ".cursor", "skills");
+  mkdirSync(cursorSkills, { recursive: true });
+  symlinkSync(skillDir, join(cursorSkills, "demo"), "dir");
   saveUserOverrides(join(tmp, ".skillhub", "overrides.json"), {
     notesOverrides: { demo: "portable note" },
     managedSkills: { demo: "external-manager" },
@@ -108,6 +114,16 @@ test("registry uses configured agent triggers and metadata overrides", (t) => {
   assert.equal(reg.skills.demo.triggers.codex, "$demo");
   assert.equal(reg.skills.demo.triggers.cursor, "/demo");
 
+  // Take the link away and the trigger word goes with it. An Agent that cannot
+  // reach the Skill has no command to offer, and printing one sends the user to
+  // type something that does nothing — which is what `unlink` and a restore
+  // from the trash both used to leave behind.
+  rmSync(join(cursorSkills, "demo"));
+  const afterUnlink = buildRegistry(tmp);
+  assert.equal(afterUnlink.skills.demo.agents.cursor, false);
+  assert.equal(afterUnlink.skills.demo.triggers.cursor, undefined);
+  assert.equal(afterUnlink.skills.demo.triggers.codex, "$demo", "the native Agent still reaches it");
+
   // An Agent that is not in use is left out of the registry entirely, so the
   // switch means the same thing to `scan`, to the sync planner and to the
   // dashboard.