feat(ghost-drift): add --gate mode to compare for deterministic ledger reconciliation

.changeset/add-compare-gate-mode.md

@@ -0,0 +1,5 @@
+---
+"ghost-drift": minor
+---
+
+Add `--gate` mode to `ghost-drift compare` that reads `.ghost-sync.json` and reports per-dimension verdicts (aligned / covered / reconverging / uncovered). Exits 0 when no uncovered drift, 1 when uncovered, 2 on hard error. Versioned JSON output via `--format json` (schema: `ghost.compare.gate/v1`). Composes over existing `compareFingerprints`, `readSyncManifest`, and `checkBounds` — no new orchestration.

apps/docs/src/generated/cli-manifest.json

@@ -1,5 +1,5 @@
 {
-  "generatedAt": "2026-05-19T14:36:11.941Z",
+  "generatedAt": "2026-05-19T16:33:13.019Z",
   "tools": [
     {
       "tool": "ghost",
@@ -265,6 +265,30 @@
               "takesValue": true,
               "negated": false
             },
+            {
+              "rawName": "--gate",
+              "name": "gate",
+              "description": "Reconcile against a sync manifest and emit a structured pass/fail verdict (N=2 only)",
+              "default": null,
+              "takesValue": false,
+              "negated": false
+            },
+            {
+              "rawName": "--sync <path>",
+              "name": "sync",
+              "description": "Sync manifest path for --gate (default: ./.ghost-sync.json)",
+              "default": null,
+              "takesValue": true,
+              "negated": false
+            },
+            {
+              "rawName": "--max-divergence-days <n>",
+              "name": "maxDivergenceDays",
+              "description": "For --gate: flag diverging dimensions older than this many days as uncovered",
+              "default": null,
+              "takesValue": true,
+              "negated": false
+            },
             {
               "rawName": "--format <fmt>",
               "name": "format",

packages/ghost/src/cli.ts

@@ -24,6 +24,7 @@ import {
   formatTemporalComparisonJSON,
   readHistory,
   readSyncManifest,
+  runGateCli,
   runGhostDriftCheck,
 } from "./core/index.js";
 import {
@@ -56,9 +57,34 @@ export function buildCli(): ReturnType<typeof cac> {
       "--history-dir <dir>",
       "Directory containing .ghost/history.jsonl (for --temporal, defaults to cwd)",
     )
+    .option(
+      "--gate",
+      "Reconcile against a sync manifest and emit a structured pass/fail verdict (N=2 only)",
+    )
+    .option(
+      "--sync <path>",
+      "Sync manifest path for --gate (default: ./.ghost-sync.json)",
+    )
+    .option(
+      "--max-divergence-days <n>",
+      "For --gate: flag diverging dimensions older than this many days as uncovered",
+    )
     .option("--format <fmt>", "Output format: cli or json", { default: "cli" })
     .action(async (fingerprints: string[], opts) => {
       try {
+        if (opts.gate) {
+          await runGateCli({
+            fingerprints,
+            cwd: process.cwd(),
+            sync: opts.sync,
+            format: opts.format,
+            maxDivergenceDays: opts.maxDivergenceDays,
+            loadFingerprint: loadComparableFingerprint,
+            compare,
+          });
+          return;
+        }
+
         const exprs = await Promise.all(
           fingerprints.map((path) => loadComparableFingerprint(path)),
         );