feat: centralized SOUL.md, mosaic-init generator, and unified launcher

- Add SOUL.md.template with {{PLACEHOLDERS}} for interactive generation
- Add mosaic-init (bash + PS1) for interactive SOUL.md creation with flag overrides
- Add mosaic launcher (bash + PS1) — unified CLI for claude/opencode/codex with SOUL.md injection
- Add codex runtime adapter (runtime/codex/instructions.md)
- Update runtime adapters (claude, opencode) with SOUL.md read directive
- Update mosaic-link-runtime-assets to push codex adapter to ~/.codex/
- Update installers to prompt for mosaic init when SOUL.md is missing

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

bin/mosaic-link-runtime-assets.ps1

@@ -93,5 +93,14 @@ if (Test-Path $opencodeSrc) {
     Copy-FileManaged $opencodeSrc $opencodeDst
 }
 
+# Codex runtime adapter
+$codexSrc = Join-Path $MosaicHome "runtime\codex\instructions.md"
+if (Test-Path $codexSrc) {
+    $codexDir = Join-Path $env:USERPROFILE ".codex"
+    if (-not (Test-Path $codexDir)) { New-Item -ItemType Directory -Path $codexDir -Force | Out-Null }
+    $codexDst = Join-Path $codexDir "instructions.md"
+    Copy-FileManaged $codexSrc $codexDst
+}
+
 Write-Host "[mosaic-link] Runtime assets synced (non-symlink mode)"
 Write-Host "[mosaic-link] Canonical source: $MosaicHome"