chore(release): bump version to 0.5.16

[its-saffron]

Version bump for release v0.5.16. The release will be published after this PR passes the required checks and merges.

dispatch 0.5.16

Highlights

In-app scheduler (retires external cron/heartbeat). Scheduled sync, the
groomer, PR follow-up, and closed-issue pruning now run on internal timers
inside the app process instead of external CronJobs. Opt in with
DISPATCH_SCHEDULER_ENABLED=true. Once enabled, you can retire the
dispatch-heartbeat cron. (#515, #520)

• Per-job intervals are overridable; set any to 0 to disable that job:
  • DISPATCH_SYNC_INTERVAL_MS (default 15m)
  • DISPATCH_GROOMER_INTERVAL_MS (default 10m)
  • DISPATCH_PR_FOLLOWUP_INTERVAL_MS (default 15m)
  • DISPATCH_PRUNE_CLOSED_INTERVAL_MS (default daily)
• Startup is delayed by DISPATCH_SCHEDULER_STARTUP_DELAY_MS so migrations
  finish first. Left disabled, dev/CI never spin timers.

Closed issues always move to status/done. Sync now enforces the terminal
status: a closed issue has its status label reconciled to status/done (and
other status/* labels stripped) directly on GitHub, so the next sync can't
revert it. (#521)

Schema-constrained groomer output. The groomer requests json_schema
responses (with the lane enum built from your configured lanes) and falls back
to json_object on a 400. This lets smaller models — e.g. a 4B — groom
reliably. (#516)

Groomer runs are serialized. A DB-backed lock (reusing the sync_lock
table) prevents overlapping groomer runs. (#517)

Fixes & internals

• Prisma client is generated on postinstall only when the schema is present,
  fixing Docker builds where npm ci runs before the schema is copied. (chore(db): generate prisma client on postinstall #512)
• Shared isStatusLabel guard across routes; tighter $transaction adapter
  cast; removed dead lane-classification code and the unused effect
  dependency. (refactor(routes): share the isStatusLabel guard #518, refactor(prisma): tighten the $transaction adapter cast #519, refactor(lane): remove dead lane-classification code #522, chore(deps): remove unused effect dependency #513)

Tests

• Coverage for the agent queue/next-task fetch path and the DB-backed global
  sync mutex. (test(agent-queue-fetch): cover the queue/next-task fetch path #524)

Dependencies

• Next.js 16.2.9 → 16.2.10 (fix(deps): update nextjs monorepo (16.2.9 → 16.2.10) #497); lucide-react 1.22.0 → 1.23.0 (feat(deps): update dependency lucide-react (1.22.0 → 1.23.0) #496)