chore: add dev boot profiling and benchmark scripts (#87940)
## Summary
Development scripts for profiling and benchmarking Next.js dev server boot time.
### Benchmarking Scripts
- `benchmark-boot-time.sh` - Wall-clock benchmarking with two metrics:
- **Listen time**: When TCP port accepts connections
- **Ready time**: When first HTTP request succeeds
- `benchmark-next-dev-boot.js` - Multi-iteration benchmarking with statistics (median, p95, stddev)
### Profiling Scripts
- `profile-next-dev-boot.js` - CPU profiling infrastructure using V8 inspector
- `analyze-profile.js` - Analyze CPU profiles to identify hot modules by CPU time
### Analysis Scripts
- `analyze-dev-server-bundle.js` - Bundle analyzer for dev server (generates treemap report)
- `trace-cli-startup.js` - Module loading trace to identify slow imports
## Usage
```bash
# Benchmark dev server boot time (5 runs by default)
./scripts/benchmark-boot-time.sh
# Multi-iteration benchmark with stats
node scripts/benchmark-next-dev-boot.js --iterations 10
# Generate CPU profile
node scripts/profile-next-dev-boot.js
# Analyze profile output
node scripts/analyze-profile.js .next/cpu-profiles/*.cpuprofile
# Analyze dev server bundle
node scripts/analyze-dev-server-bundle.js --open
```
## Test Plan
- [x] Run `./scripts/benchmark-boot-time.sh` locally
- [x] Verify scripts execute without errors
