fix(uninstall): wildcard env cleanup + AUTH_TOKEN + npm + claude README (Item 18)

User asked: do per-tool READMEs document uninstall? Sub-agent audit
(gpt-5.5 sh + glm-5.1 ps1) found multiple BLOCKERs in uninstall scripts.

Fixes:

1. claude/README.md — added Uninstall section (was missing — other tools'
   READMEs already documented theirs).

2. All 4 ps1 uninstallers (claude/codex/gemini/qwen) — wildcard env-var
   cleanup by prefix. Was: hardcoded list missed *_AUTH_TOKEN, leaving
   stale token after uninstall → Auth conflict warning on reinstall
   (root cause user reported on Windows).
   Prefixes:
     claude → ANTHROPIC_*, CLAUDE_*, DISABLE_TELEMETRY, ...
     codex  → OPENAI_*
     gemini → GEMINI_*, GOOGLE_API_KEY, GOOGLE_CLOUD_PROJECT
     qwen   → QWEN_*, DASHSCOPE_*

3. codex/ucodex_uninstall.ps1 — added `npm uninstall -g @openai/codex`
   step (was missing — npm package would survive uninstall).

4. codex/ucodex_uninstall.ps1 — also clears npm registry override
   `@openai:registry`.

Audit also flagged (NOT applied — defer to next iteration):
- sh: overly broad `sed '/PATTERN/d'` deletes unrelated user lines
  (could damage user's .bashrc — use marker comments instead)
- sh: missing /var/root scan (macOS root user)
- sh: missing systemd/LaunchAgent cleanup
- sh: backup restore not implemented
- All: should preserve some user data (history, projects) — current
  behavior is destructive

Tests: tests/test_uninstall_completeness.py — 10 GREEN regression guards
(prefix wildcard works, README has section, sh uses portable sed,
codex npm uninstall present).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

qwen/uqwen_uninstall.ps1

@@ -29,6 +29,21 @@ if (Test-Path $qwenDir) {
 # ---- Remove env vars ----
 
 Write-Host "  Removing environment variables..." -ForegroundColor Cyan
+# >>> wildcard env cleanup (Item 18 audit) <<<
+$prefixesToRemove = @("QWEN_", "DASHSCOPE_")
+$userVars = [System.Environment]::GetEnvironmentVariables("User")
+foreach ($name in @($userVars.Keys)) {
+    foreach ($p in $prefixesToRemove) {
+        if ($name -like "${p}*" -or $name -eq $p) {
+            [System.Environment]::SetEnvironmentVariable($name, $null, "User")
+            Remove-Item -Path "Env:\$name" -ErrorAction SilentlyContinue
+            Write-Host "  Removed env: $name" -ForegroundColor Cyan
+            break
+        }
+    }
+}
+# <<< end wildcard cleanup >>>
+
 [System.Environment]::SetEnvironmentVariable("QWEN_API_KEY", $null, "User")
 [System.Environment]::SetEnvironmentVariable("QWEN_BASE_URL", $null, "User")
 Remove-Item Env:QWEN_API_KEY -ErrorAction SilentlyContinue