feat: introduce Forever Mode (Sisyphus, Confucius, and Bicameral Voice)

- Sisyphus: auto-resume timer with schedule_work tool
- Confucius: built-in sub-agent for knowledge consolidation before compression
- Hippocampus: in-memory short-term memory via background micro-consolidation
- Bicameral Voice: proactive knowledge alignment on user input
- Archive compression mode for long-running sessions
- Onboarding dialog for first-time Forever Mode setup
- Refresh system instruction per turn so hippocampus reaches the model

schemas/settings.schema.json

@@ -181,6 +181,13 @@
               "markdownDescription": "Minimum retention period (safety limit, defaults to \"1d\")\n\n- Category: `General`\n- Requires restart: `no`\n- Default: `1d`",
               "default": "1d",
               "type": "string"
+            },
+            "warningAcknowledged": {
+              "title": "Warning Acknowledged",
+              "description": "Whether the user has acknowledged the session retention warning",
+              "markdownDescription": "Whether the user has acknowledged the session retention warning\n\n- Category: `General`\n- Requires restart: `no`\n- Default: `false`",
+              "default": false,
+              "type": "boolean"
             }
           },
           "additionalProperties": false