tools-sync: 修复会删掉宿主自装 skill 的 registry 对账缺陷

本次同步实跑触发了数据丢失：orca-cli 的物理副本在 ~\.agents\skills（Orca 就是
这样装的——真目录放 .agents，再把每个工具链过去，本机 8 个工具全指向它），
而主副本里的同名条目本身是指向它的 junction。对账循环从不检查"主副本条目是不是
链接"，于是 fingerprint 比对经链接解析到同一份内容判为"identical"，删掉 registry
副本并建 junction → 主副本与 registry 互指成环，唯一的真副本没了。
orchestration 走 INGEST 分支，则把 Orca 的布局反了过来。

两者均已用 `orca skills install --skill <name>` 恢复为 Orca 自己的布局。

修复三处：
- 对账循环：主副本条目本身是链接时，判定该 skill 归宿主所有，计入 foreign 跳过。
- INGEST：新增 Get-SkillDirLinkers，若 ~\.* 下其他工具的 skills 目录有链接指向
  这个目录，说明它是宿主自装 skill 的物理家，不搬进主副本。
- 镜像阶段：跳过本身是链接的主副本条目，否则 Codex 会把同一 skill 注册两遍
  （.agents 与 .codex 都在扫）。

回归测试新增 hostowned 夹具（真目录在 registry、主副本是链接）：在修复前的脚本上
以"real dir was collapsed into a link"失败，修复后通过。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01438Zbcx49e4o46uSA71mFF

tools-sync/scripts/sync_repos.ps1

@@ -117,6 +117,28 @@ function Get-DirFingerprint([string]$Path) {
     return (($lines | Sort-Object) -join "`n")
 }
 
+# Agent tools each keep their own skills directory and a host installer may pick any one of them
+# as a skill's physical home, linking the rest at it. Finding those linkers is how we tell a
+# host-installed skill from one authored on the Codex side.
+function Get-SkillDirLinkers([string]$TargetPath) {
+    $roots = @()
+    foreach ($d in Get-ChildItem $env:USERPROFILE -Directory -Force -ErrorAction SilentlyContinue |
+                   Where-Object { $_.Name -like ".*" }) {
+        foreach ($sub in @("skills", "agent\skills")) {
+            $cand = Join-Path $d.FullName $sub
+            if (Test-Path $cand) { $roots += $cand }
+        }
+    }
+    $hits = @()
+    foreach ($r in $roots) {
+        if (Test-UnderPath $TargetPath $r) { continue }   # the home itself
+        $link = Join-Path $r (Split-Path $TargetPath -Leaf)
+        $item = Get-Item -LiteralPath $link -Force -ErrorAction SilentlyContinue
+        if ($item -and (Test-IsLink $item) -and ((Get-LinkTarget $item) -eq $TargetPath)) { $hits += $r }
+    }
+    return $hits
+}
+
 function New-SkillJunction([string]$LinkPath, [string]$TargetPath, [string]$Why) {
     if ($DryRun) { Write-Host "  (dry-run) would link $LinkPath -> $TargetPath  [$Why]"; return }
     New-Item -ItemType Junction -Path $LinkPath -Target $TargetPath | Out-Null
@@ -272,6 +294,17 @@ foreach ($reg in $registries) {
         $name = Split-Path $copyPath -Leaf
         $primaryPath = Join-Path $ClaudeSkills $name
         if (-not (Test-Path $copyPath)) { continue }   # already resolved earlier this run
+
+        # The primary entry is itself a link into a registry: this skill's physical home is the
+        # registry, and the host installed it that way round (Orca does exactly this - it puts the
+        # real directory in ~\.agents\skills and links every tool at it). Collapsing the registry
+        # copy here would point the link at itself and DELETE the only copy. Leave it to its owner.
+        $primaryItem = Get-Item -LiteralPath $primaryPath -Force -ErrorAction SilentlyContinue
+        if ($primaryItem -and (Test-IsLink $primaryItem)) {
+            $foreign++
+            continue
+        }
+
         $repairLinks += $copyPath
 
         # --- real directory holding a skill ---
@@ -287,6 +320,15 @@ foreach ($reg in $registries) {
                 Write-Host "  registry-only skill NOT ingested (-NoIngest): $name"
                 continue
             }
+            # Other agent tools linking at this directory mean it is a host-installed skill's
+            # physical home, not a skill authored here. Moving it inverts the host's layout and
+            # its own updater then fights us for the location.
+            $linkers = Get-SkillDirLinkers $copyPath
+            if ($linkers) {
+                $script:Notes += "$name lives in $copyPath and $($linkers.Count) other tool registr$(if ($linkers.Count -eq 1) { 'y links' } else { 'ies link' }) at it; treated as host-installed and left alone."
+                Write-Host "  host-installed skill (linked from $($linkers.Count) other tool(s)), not ingested: $name"
+                continue
+            }
             Write-Host "  INGEST registry-only skill: $name  ($copyPath -> $primaryPath)"
             if (-not $DryRun) { Move-Item -LiteralPath $copyPath -Destination $primaryPath }
             $script:Ingested += $name
@@ -332,7 +374,10 @@ if ($MirrorRegistry) {
         if (-not $DryRun) { Remove-Item -Recurse -Force $mirrorGit }
     }
 
-    $primarySkills = Get-ChildItem $ClaudeSkills -Directory | Where-Object { $_.Name -notlike ".*" }
+    # A primary entry that is itself a link belongs to whichever host installed it (its real home
+    # is a registry the host already exposes to Codex). Mirroring it would register it twice.
+    $primarySkills = Get-ChildItem $ClaudeSkills -Directory -Force |
+        Where-Object { $_.Name -notlike ".*" -and -not (Test-IsLink $_) }
     foreach ($d in $primarySkills) {
         $link = Join-Path $MirrorRegistry $d.Name
         if (Test-Path $link) { continue }