phase15: update CLAUDE.md and sync with current progress

- Update phase indicator to Phase 15 (Self-Hosting)
- Update documentation links to Phase 15 resources
- Reflect completion of R1-R5 tasks and ongoing work
- Fix CURRENT_TASK.md location to root directory

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

tools/ny_parser_run.ps1

@@ -0,0 +1,6 @@
+Param()
+$ErrorActionPreference = 'Stop'
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+$root = Join-Path $here '..' | Resolve-Path
+
+& (Join-Path $root 'target\release\nyash.exe') (Join-Path $root 'apps\ny-parser-nyash\main.nyash')