fix(plugins): replace dependency marker files with a real satisfaction check

The .dependencies_installed hash-marker system only tracked "was this exact
requirements.txt hashed before" — not whether the packages it names are
actually present. That made it fragile (a wiped venv, a manually removed
package, or a lost/corrupted marker forces a needless full pip reinstall or,
worse, a false skip) and produced dead weight for the ~10 plugins whose
requirements.txt is comment-only (they still paid a pip subprocess on first
boot before a marker existed).

Replace it with requirements_are_satisfied() in plugin_loader.py, which
checks each real requirement line against importlib.metadata directly, so
install_dependencies() only shells out to pip when something is actually
missing or version-mismatched. Drops the marker file entirely: removed all
marker read/write sites in plugin_loader.py and store_manager.py, the
now-pointless marker-cleanup step in the git-update path, the unused legacy
marker implementation in plugin_manager.py, and the already-stale
clear_dependency_markers.sh script.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEZK1P1Q1fu5pcuVrkrCFZ

src/plugin_system/store_manager.py

@@ -5,7 +5,6 @@ Handles plugin discovery, installation, updates, and uninstallation
 from both the official registry and custom GitHub repositories.
 """
 
-import hashlib
 import os
 import re
 import json
@@ -26,6 +25,7 @@ import logging
 from urllib.parse import urlparse
 
 from src.common.permission_utils import sudo_remove_directory, install_requirements_file
+from src.plugin_system.plugin_loader import requirements_has_real_deps, requirements_are_satisfied
 
 try:
     from jsonschema import Draft7Validator, ValidationError
@@ -1912,7 +1912,15 @@ class PluginStoreManager:
         if not requirements_file.exists():
             self.logger.debug(f"No requirements.txt found in {plugin_path.name}")
             return True
-        
+
+        if not requirements_has_real_deps(str(requirements_file)):
+            self.logger.debug(f"requirements.txt for {plugin_path.name} has no real dependencies, skipping pip")
+            return True
+
+        if requirements_are_satisfied(str(requirements_file)):
+            self.logger.debug(f"Dependencies for {plugin_path.name} already satisfied, skipping pip")
+            return True
+
         try:
             self.logger.info(f"Installing dependencies for {plugin_path.name}")
             # Routed through the shared root-visible installer (same one the
@@ -1929,12 +1937,6 @@ class PluginStoreManager:
                 )
                 return False
             self.logger.info(f"Dependencies installed successfully for {plugin_path.name}")
-            # Write hash marker so plugin_loader skips redundant pip run on next startup
-            try:
-                current_hash = hashlib.sha256(requirements_file.read_bytes()).hexdigest()
-                (plugin_path / ".dependencies_installed").write_text(current_hash, encoding='utf-8')
-            except OSError as marker_err:
-                self.logger.debug("Could not write dependency marker for %s: %s", plugin_path.name, marker_err)
             return True
 
         except subprocess.TimeoutExpired:
@@ -2432,19 +2434,6 @@ class PluginStoreManager:
                                     file_path = line[3:].strip()
                                     untracked_files.append(file_path)
                         
-                        # Remove marker files that are safe to delete (they'll be regenerated)
-                        safe_to_remove = ['.dependencies_installed']
-                        removed_files = []
-                        for file_name in safe_to_remove:
-                            file_path = plugin_path / file_name
-                            if file_path.exists() and file_name in untracked_files:
-                                try:
-                                    file_path.unlink()
-                                    removed_files.append(file_name)
-                                    self.logger.info(f"Removed marker file {file_name} from {plugin_id} before update")
-                                except Exception as e:
-                                    self.logger.warning(f"Could not remove {file_name} from {plugin_id}: {e}")
-                        
                         # Check for tracked file changes
                         status_result = subprocess.run(
                             ['git', '-C', str(plugin_path), 'status', '--porcelain', '--untracked-files=no'],
@@ -2455,10 +2444,9 @@ class PluginStoreManager:
                         )
                         has_changes = bool(status_result.stdout.strip())
                         
-                        # If there are remaining untracked files (not safe to remove), stash them
-                        remaining_untracked = [f for f in untracked_files if f not in removed_files]
-                        if remaining_untracked:
-                            self.logger.info(f"Found {len(remaining_untracked)} untracked files in {plugin_id}, will stash them")
+                        # If there are untracked files, stash them
+                        if untracked_files:
+                            self.logger.info(f"Found {len(untracked_files)} untracked files in {plugin_id}, will stash them")
                             has_changes = True
                     except subprocess.TimeoutExpired:
                         # If status check times out, assume there might be changes and proceed