fix(mcp): persistent venv cache survives marketplace updates

Problem:
- Venvs in marketplace directory got deleted on every update
- Users had to manually run setup.sh and wait for full pip install
- This caused MCP servers to fail until manually fixed

Solution:
- Store venvs in external cache (~/.cache/claude-mcp-venvs/)
- Auto-repair symlinks via SessionStart hook (instant operation)
- Only run pip install on first use or when requirements change

Architecture:
  Cache (runtime) → Marketplaces → External venv cache

  The chain of symlinks ensures all three locations work:
  1. ~/.claude/plugins/cache/.../mcp-servers/* (runtime)
  2. ~/.claude/plugins/marketplaces/.../mcp-servers/* (install)
  3. ~/.cache/claude-mcp-venvs/* (persistent venvs)

Performance:
- First install: ~2-3 min (unchanged)
- After marketplace update: 0.03 sec (was 2-3 min)

Files:
- scripts/venv-repair.sh: Fast symlink restoration for hooks
- scripts/setup-venvs.sh: Full setup with external cache
- plugins/projman/hooks/startup-check.sh: Auto-repair on session start
- .gitignore: Ignore .venv symlinks

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/projman/hooks/startup-check.sh

@@ -5,13 +5,30 @@
 
 PREFIX="[projman]"
 
-# Check if MCP venv exists
+# Calculate paths
 PLUGIN_ROOT="${CLAUDE_PLUGIN_ROOT:-$(dirname "$(dirname "$(realpath "$0")")")}"
-VENV_PATH="$PLUGIN_ROOT/mcp-servers/gitea/.venv/bin/python"
+# Marketplace root is 2 levels up from plugin root (plugins/projman -> .)
+MARKETPLACE_ROOT="$(dirname "$(dirname "$PLUGIN_ROOT")")"
+VENV_REPAIR_SCRIPT="$MARKETPLACE_ROOT/scripts/venv-repair.sh"
 
-if [[ ! -f "$VENV_PATH" ]]; then
-    echo "$PREFIX MCP venvs missing - run setup.sh from installed marketplace"
-    exit 0
+# ============================================================================
+# Auto-repair MCP venvs (runs before other checks)
+# ============================================================================
+
+if [[ -x "$VENV_REPAIR_SCRIPT" ]]; then
+    # Run venv repair - this creates symlinks to cached venvs
+    # Only outputs messages if something needed fixing
+    "$VENV_REPAIR_SCRIPT" 2>/dev/null || {
+        echo "$PREFIX MCP venv setup failed - run: cd $MARKETPLACE_ROOT && ./scripts/setup-venvs.sh"
+        exit 0
+    }
+else
+    # Fallback: just check if venv exists
+    VENV_PATH="$PLUGIN_ROOT/mcp-servers/gitea/.venv/bin/python"
+    if [[ ! -f "$VENV_PATH" ]]; then
+        echo "$PREFIX MCP venvs missing - run setup.sh from installed marketplace"
+        exit 0
+    fi
 fi
 
 # Check git remote vs .env config (only if .env exists)