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-sync-skills.ps1

@@ -0,0 +1,126 @@
+# mosaic-sync-skills.ps1
+# Syncs canonical skills and links them into agent runtime skill directories.
+# Uses directory junctions (no elevation required) with fallback to copies.
+# PowerShell equivalent of mosaic-sync-skills (bash).
+$ErrorActionPreference = "Stop"
+
+param(
+    [switch]$LinkOnly,
+    [switch]$NoLink,
+    [switch]$Help
+)
+
+$MosaicHome = if ($env:MOSAIC_HOME) { $env:MOSAIC_HOME } else { Join-Path $env:USERPROFILE ".config\mosaic" }
+$SkillsRepoUrl = if ($env:MOSAIC_SKILLS_REPO_URL) { $env:MOSAIC_SKILLS_REPO_URL } else { "https://git.mosaicstack.dev/mosaic/agent-skills.git" }
+$SkillsRepoDir = if ($env:MOSAIC_SKILLS_REPO_DIR) { $env:MOSAIC_SKILLS_REPO_DIR } else { Join-Path $MosaicHome "sources\agent-skills" }
+$MosaicSkillsDir = Join-Path $MosaicHome "skills"
+$MosaicLocalSkillsDir = Join-Path $MosaicHome "skills-local"
+
+if ($Help) {
+    Write-Host @"
+Usage: mosaic-sync-skills.ps1 [-LinkOnly] [-NoLink] [-Help]
+
+Sync canonical skills into ~/.config/mosaic/skills and link all Mosaic skills
+into runtime skill directories using directory junctions.
+
+Options:
+  -LinkOnly     Skip git clone/pull and only relink
+  -NoLink       Sync canonical skills but do not update runtime links
+  -Help         Show help
+"@
+    exit 0
+}
+
+foreach ($d in @($MosaicHome, $MosaicSkillsDir, $MosaicLocalSkillsDir)) {
+    if (-not (Test-Path $d)) { New-Item -ItemType Directory -Path $d -Force | Out-Null }
+}
+
+# Fetch skills from git
+if (-not $LinkOnly) {
+    if (Test-Path (Join-Path $SkillsRepoDir ".git")) {
+        Write-Host "[mosaic-skills] Updating skills source: $SkillsRepoDir"
+        git -C $SkillsRepoDir pull --rebase
+    }
+    else {
+        Write-Host "[mosaic-skills] Cloning skills source to: $SkillsRepoDir"
+        $parentDir = Split-Path $SkillsRepoDir -Parent
+        if (-not (Test-Path $parentDir)) { New-Item -ItemType Directory -Path $parentDir -Force | Out-Null }
+        git clone $SkillsRepoUrl $SkillsRepoDir
+    }
+
+    $sourceSkillsDir = Join-Path $SkillsRepoDir "skills"
+    if (-not (Test-Path $sourceSkillsDir)) {
+        Write-Host "[mosaic-skills] Missing source skills dir: $sourceSkillsDir" -ForegroundColor Red
+        exit 1
+    }
+
+    # Sync: remove old, copy new
+    if (Test-Path $MosaicSkillsDir) {
+        Get-ChildItem $MosaicSkillsDir | Remove-Item -Recurse -Force
+    }
+    Copy-Item "$sourceSkillsDir\*" $MosaicSkillsDir -Recurse -Force
+}
+
+if (-not (Test-Path $MosaicSkillsDir)) {
+    Write-Host "[mosaic-skills] Canonical skills dir missing: $MosaicSkillsDir" -ForegroundColor Red
+    exit 1
+}
+
+if ($NoLink) {
+    Write-Host "[mosaic-skills] Canonical sync completed (link update skipped)"
+    exit 0
+}
+
+function Link-SkillIntoTarget {
+    param([string]$SkillPath, [string]$TargetDir)
+
+    $name = Split-Path $SkillPath -Leaf
+    if ($name.StartsWith(".")) { return }
+
+    $linkPath = Join-Path $TargetDir $name
+
+    # Already a junction/symlink — recreate
+    $existing = Get-Item $linkPath -Force -ErrorAction SilentlyContinue
+    if ($existing -and ($existing.Attributes -band [System.IO.FileAttributes]::ReparsePoint)) {
+        Remove-Item $linkPath -Force
+    }
+    elseif ($existing) {
+        Write-Host "[mosaic-skills] Preserve existing runtime-specific entry: $linkPath"
+        return
+    }
+
+    # Try junction first, fall back to copy
+    try {
+        New-Item -ItemType Junction -Path $linkPath -Target $SkillPath -ErrorAction Stop | Out-Null
+    }
+    catch {
+        Write-Host "[mosaic-skills] Junction failed for $name, falling back to copy"
+        Copy-Item $SkillPath $linkPath -Recurse -Force
+    }
+}
+
+$linkTargets = @(
+    (Join-Path $env:USERPROFILE ".claude\skills"),
+    (Join-Path $env:USERPROFILE ".codex\skills"),
+    (Join-Path $env:USERPROFILE ".config\opencode\skills")
+)
+
+foreach ($target in $linkTargets) {
+    if (-not (Test-Path $target)) { New-Item -ItemType Directory -Path $target -Force | Out-Null }
+
+    # Link canonical skills
+    Get-ChildItem $MosaicSkillsDir -Directory | ForEach-Object {
+        Link-SkillIntoTarget $_.FullName $target
+    }
+
+    # Link local skills
+    if (Test-Path $MosaicLocalSkillsDir) {
+        Get-ChildItem $MosaicLocalSkillsDir -Directory | ForEach-Object {
+            Link-SkillIntoTarget $_.FullName $target
+        }
+    }
+
+    Write-Host "[mosaic-skills] Linked skills into: $target"
+}
+
+Write-Host "[mosaic-skills] Complete"