feat: unified first-run flow — merge wizard + gateway install (IUH-M03)

Collapse `mosaic wizard` and `mosaic gateway install` into a single cohesive
first-run experience. Gateway config and admin bootstrap now run as terminal
stages of `runWizard`, sharing `WizardState` with the framework stages and
eliminating the fragile 10-minute `$XDG_RUNTIME_DIR/mosaic-install-state.json`
session-file bridge.

- Extract `gatewayConfigStage` and `gatewayBootstrapStage` as first-class
  wizard stages with full spec coverage (headless + interactive paths).
- `mosaic gateway install` becomes a thin wrapper that invokes the same
  two stages — the CLI entry point is preserved for operators who only
  need to (re)configure the daemon.
- Honor explicit `--port` override even on resume: when the override
  differs from the saved GATEWAY_PORT, force a config regeneration so
  `.env` and `meta.json` cannot drift.
- Honor `state.hooks.accepted === false` in the finalize stage and in
  `mosaic-link-runtime-assets`: declined hooks are now actually opted-out,
  with a stable `mosaic-managed: true` marker in the template so cleanup
  survives template updates without touching user-owned configs.
- Headless rerun of an already-bootstrapped gateway with no local token
  cache is a successful no-op (no more false-positive install failures).
- `tools/install.sh` calls `mosaic wizard` only — the follow-up
  `mosaic gateway install` auto-launch is removed.

Closes mosaicstack/mosaic-stack#427.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/mosaic/framework/runtime/claude/hooks-config.json

@@ -1,6 +1,7 @@
 {
   "name": "Universal Atomic Code Implementer Hooks",
   "description": "Comprehensive hooks configuration for quality enforcement and automatic remediation",
+  "mosaic-managed": true,
   "version": "1.0.0",
   "hooks": {
     "PostToolUse": [