chore: remove serena leftovers (hooks, permissions, docs, templates)

Serena MCP was removed from the project, but config and docs still
referenced it — the SessionStart hook failed every session with
"serena-hooks: not found".

- .claude/settings.json: drop serena-hooks hooks (PreToolUse,
  SessionStart, Stop) and the mcp__serena__* permission
- .serena/: delete tracked project files and memories
- CLAUDE.md: drop the Serena tool section, keep Context7
- agentic/commands/: replace serena tool references with built-in
  Glob/Grep/Read/Edit equivalents in the audit/prime/agentic templates

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: MarkusNeusinger

.claude/settings.json

@@ -8,7 +8,6 @@
       "Read(/tmp/*)",
       "mcp__plugin_context7_context7__*",
       "mcp__plugin_playwright_playwright__*",
-      "mcp__serena__*",
       "Bash(git commit *)",
       "Bash(git push *)"
     ],
@@ -17,49 +16,5 @@
   },
   "env": {
     "CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS": "1"
-  },
-  "hooks": {
-    "PreToolUse": [
-      {
-        "matcher": "",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "serena-hooks remind --client=claude-code"
-          }
-        ]
-      },
-      {
-        "matcher": "mcp__serena__*",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "serena-hooks auto-approve --client=claude-code"
-          }
-        ]
-      }
-    ],
-    "SessionStart": [
-      {
-        "matcher": "",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "serena-hooks activate --client=claude-code"
-          }
-        ]
-      }
-    ],
-    "Stop": [
-      {
-        "matcher": "",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "serena-hooks cleanup --client=claude-code"
-          }
-        ]
-      }
-    ]
   }
 }