feat!: unify mosaic CLI — native launcher, no bin/ directory

BREAKING CHANGE: ~/.config/mosaic/bin/ is removed entirely.
The mosaic npm CLI is now the only executable.

## What changed

- **bin/ → deleted**: All scripts moved to tools/_scripts/ (internal)
- **mosaic-launch → deleted**: Launcher logic is native TypeScript
  in packages/cli/src/commands/launch.ts
- **mosaic.ps1 → deleted**: PowerShell launcher removed
- **Framework install.sh**: Complete rewrite with migration system
- **Version tracking**: .framework-version file (schema v2)
- **Migration v1→v2**: Auto-removes bin/, cleans old PATH entries
  from shell profiles

## Native TypeScript launcher (commands/launch.ts)

All runtime launch logic ported from bash:
- Runtime prompt builder (AGENTS.md + RUNTIME.md + USER.md + TOOLS.md)
- Mission context injection (reads .mosaic/orchestrator/mission.json)
- PRD status injection (scans docs/PRD.md)
- Pre-flight checks (MOSAIC_HOME, AGENTS.md, SOUL.md, runtime binary)
- Session lock management with signal cleanup
- Per-runtime launch: Claude, Codex, OpenCode, Pi
- Yolo mode flags per runtime
- Pi skill discovery + extension loading
- Framework management (init, doctor, sync, bootstrap) delegates
  to tools/_scripts/ bash implementations

## Installer

- tools/install.sh: detects framework by .framework-version or AGENTS.md
- Framework install.sh: migration system with schema versioning
- Forward-compatible: add migrations as numbered blocks
- No PATH manipulation for framework (npm bin is the only PATH entry)

packages/mosaic/framework/tools/_scripts/mosaic-release-upgrade.ps1

@@ -0,0 +1,65 @@
+# mosaic-release-upgrade.ps1 — Upgrade installed Mosaic framework release (Windows)
+#
+# Usage:
+#   mosaic-release-upgrade.ps1
+#   mosaic-release-upgrade.ps1 -Ref main -Keep
+#   mosaic-release-upgrade.ps1 -Ref v0.2.0 -Overwrite -Yes
+#
+param(
+    [string]$Ref = $(if ($env:MOSAIC_BOOTSTRAP_REF) { $env:MOSAIC_BOOTSTRAP_REF } else { "main" }),
+    [switch]$Keep,
+    [switch]$Overwrite,
+    [switch]$Yes,
+    [switch]$DryRun
+)
+
+$ErrorActionPreference = "Stop"
+
+$MosaicHome = if ($env:MOSAIC_HOME) { $env:MOSAIC_HOME } else { Join-Path $env:USERPROFILE ".config\mosaic" }
+$RemoteInstallerUrl = if ($env:MOSAIC_REMOTE_INSTALL_URL) {
+    $env:MOSAIC_REMOTE_INSTALL_URL
+} else {
+    "https://git.mosaicstack.dev/mosaic/mosaic-stack/raw/branch/main/tools/install.sh"
+}
+
+$installMode = if ($Overwrite) { "overwrite" } elseif ($Keep) { "keep" } elseif ($env:MOSAIC_INSTALL_MODE) { $env:MOSAIC_INSTALL_MODE } else { "keep" }
+if ($installMode -notin @("keep", "overwrite")) {
+    Write-Host "[mosaic-release-upgrade] Invalid install mode: $installMode" -ForegroundColor Red
+    exit 1
+}
+
+$currentVersion = "unknown"
+$mosaicCmd = Join-Path $MosaicHome "bin\mosaic.ps1"
+if (Test-Path $mosaicCmd) {
+    try {
+        $currentVersion = (& $mosaicCmd --version) -replace '^mosaic\s+', ''
+    }
+    catch {
+        $currentVersion = "unknown"
+    }
+}
+
+Write-Host "[mosaic-release-upgrade] Current version: $currentVersion"
+Write-Host "[mosaic-release-upgrade] Target ref: $Ref"
+Write-Host "[mosaic-release-upgrade] Install mode: $installMode"
+Write-Host "[mosaic-release-upgrade] Installer URL: $RemoteInstallerUrl"
+
+if ($DryRun) {
+    Write-Host "[mosaic-release-upgrade] Dry run: no changes applied."
+    exit 0
+}
+
+if (-not $Yes) {
+    $confirmation = Read-Host "Proceed with Mosaic release upgrade? [y/N]"
+    if ($confirmation -notin @("y", "Y", "yes", "YES")) {
+        Write-Host "[mosaic-release-upgrade] Aborted."
+        exit 1
+    }
+}
+
+$env:MOSAIC_BOOTSTRAP_REF = $Ref
+$env:MOSAIC_INSTALL_MODE = $installMode
+$env:MOSAIC_HOME = $MosaicHome
+
+Invoke-RestMethod -Uri $RemoteInstallerUrl | Invoke-Expression
+