mosaic fleet logins: per-seat credential pass-through (P4 gap closure)

Measured: the npm fleet group already covers the P4 plan surface
(ps=pulse, doctor, start/stop/restart/status=seat lifecycle). The one
gap was seat-logins: adds 'fleet logins' as a pass-through to
framework/tools/fleet/seat-logins.sh (args verbatim, exit codes
preserved; static spawnSync import). Spec subcommand list also fixed
for pre-existing drift (install-systemd, migrate-v1 were unlisted);
fleet.spec 208/213 with only the stash-verified pre-existing failures.

packages/mosaic/src/commands/fleet.spec.ts

@@ -106,6 +106,7 @@ describe('registerFleetCommand', () => {
       'init',
       'install',
       'install-systemd',
+      'logins',
       'migrate-v1',
       'persona',
       'plan',

packages/mosaic/src/commands/fleet.ts

@@ -17,7 +17,7 @@ import { homedir, hostname, userInfo } from 'node:os';
 import { dirname, join, resolve } from 'node:path';
 import { fleetAgentEnvDir } from '../fleet/brain-home.js';
 import { fileURLToPath } from 'node:url';
-import { spawn } from 'node:child_process';
+import { spawn, spawnSync } from 'node:child_process';
 import * as readline from 'node:readline';
 import type { Command } from 'commander';
 import YAML from 'yaml';
@@ -1606,6 +1606,24 @@ export function registerFleetCommand(program: Command, deps: FleetCommandDeps =
     .option('--mosaic-home <path>', 'Mosaic home directory', paths.mosaicHome)
     .option('--roster <path>', 'Fleet roster path');
 
+  // fleet logins (P4 gap closure, 2026-08-29): project per-seat git tokens
+  // from the brain into usable credentials. The implementation is the
+  // framework fleet tool; args pass through verbatim (--apply --seat X).
+  cmd
+    .command('logins')
+    .description('Per-seat git credentials: seat-logins.sh pass-through (--apply --seat <name>)')
+    .allowUnknownOption(true)
+    .allowExcessArguments(true)
+    .action((...rest: unknown[]) => {
+      const cmdObj = rest[rest.length - 1] as { args: string[] };
+      const script = `${frameworkRoot}/tools/fleet/seat-logins.sh`;
+      const result = spawnSync('bash', [script, ...cmdObj.args], {
+        stdio: 'inherit',
+        env: process.env,
+      });
+      process.exit(result.status ?? 125);
+    });
+
   cmd
     .command('init')
     .description('Initialize a local fleet roster')