feat(lanes): add ccam lanes gc — orphan MCP reap + log capping (E, F3c)

Ports the two pieces of Shipyard's lane-gc.sh that match CCAM's actual
architecture: kill Playwright MCP processes reparented to pid 1 (owning
session died), cap hook logs over 10MB back to their last 2MB in place.
Drops auto-removing stale worktrees by age (conflicts with the
never-automatic-destroy rule), state archiving, and scratch-debris
sweep (different storage architecture / files CCAM doesn't generate) —
see docs/superpowers/specs/2026-08-05-lane-gc-design.md.

bin/ccam.js

@@ -1541,6 +1541,36 @@ function cmdSkillsInstall() {
   console.log(`${c.green("✔")} installed ship-feature-lane skill -> ${dest}`);
 }
 
+/**
+ * `ccam lanes gc [--dry-run]` — reap orphaned Playwright MCP processes
+ * (owning session died) and cap oversized hook logs, across every lane on
+ * this machine. Machine-wide, not one lane's; pure local process/file
+ * action, no HTTP round-trip.
+ */
+function cmdLanesGc(args) {
+  const dryRun = args.includes("--dry-run");
+  const laneGc = require(path.join(REPO_ROOT, "server", "lib", "lane-gc.js"));
+
+  const reaped = laneGc.reapOrphanMcp({ dryRun });
+  if (reaped.length) {
+    console.log(
+      `${dryRun ? "would reap" : "reaped"} ${reaped.length} orphaned MCP process(es): ${reaped.join(", ")}`
+    );
+  } else {
+    console.log("no orphaned MCP processes found");
+  }
+
+  const capped = laneGc.capOversizedLogs({ dryRun });
+  if (capped.length) {
+    for (const { path: logPath, sizeBefore } of capped) {
+      const mb = (sizeBefore / (1024 * 1024)).toFixed(1);
+      console.log(`${dryRun ? "would cap" : "capped"} ${logPath} (${mb}MB -> 2MB)`);
+    }
+  } else {
+    console.log("no oversized logs found");
+  }
+}
+
 /**
  * `ccam lanes profile init <repo>` — detect a Node.js project and scaffold
  * `.ccam/profile/`. Pure filesystem action against the SOURCE repo; does not
@@ -2433,6 +2463,11 @@ const COMMAND_GROUPS = [
         "<name> [<id>]",
         "Check whether a named integration (tracker, dev_qc, ci_wait) is on for this lane — exit 0/1",
       ],
+      [
+        "lanes gc",
+        "[--dry-run]",
+        "Reap orphaned Playwright MCP processes + cap oversized hook logs, across every lane",
+      ],
       [
         "skills install",
         "",
@@ -3265,6 +3300,9 @@ async function runCommand(argv) {
       if (rest[0] === "integration") {
         return cmdLanesIntegration(rest.slice(1));
       }
+      if (rest[0] === "gc") {
+        return cmdLanesGc(rest.slice(1));
+      }
       return cmdLanes();
     case "skills": {
       if (rest[0] === "install") return cmdSkillsInstall();