feat(lanes): extract skills-install lib, add POST /api/skills/install (F4)

bin/ccam.js

@@ -1529,16 +1529,16 @@ async function cmdLanesAdd(args) {
  * existing global copy with the current one.
  */
 function cmdSkillsInstall() {
-  const src = path.join(REPO_ROOT, ".claude", "skills", "ship-feature-lane");
-  if (!fs.existsSync(src)) {
-    console.error(`✖ not found: ${src}`);
+  const { installShipFeatureLaneSkill } = require(
+    path.join(REPO_ROOT, "server", "lib", "skills-install.js")
+  );
+  try {
+    const result = installShipFeatureLaneSkill({ repoRoot: REPO_ROOT });
+    console.log(`${c.green("✔")} installed ship-feature-lane skill -> ${result.path}`);
+  } catch (err) {
+    console.error(`✖ ${err.message}`);
     process.exitCode = 1;
-    return;
   }
-  const dest = path.join(require("node:os").homedir(), ".claude", "skills", "ship-feature-lane");
-  fs.mkdirSync(path.dirname(dest), { recursive: true });
-  fs.cpSync(src, dest, { recursive: true, force: true });
-  console.log(`${c.green("✔")} installed ship-feature-lane skill -> ${dest}`);
 }
 
 /**