chore(conductor): Add new track 'Fix RRULE UNTIL conversion'

conductor/tracks.md

@@ -16,3 +16,8 @@ This file tracks all major tracks for the project. Each track has its own detail
 
 - [x] **Track: Fix RRULE object expansion error by correctly mapping object keys to standard iCalendar RRULE properties.**
   *Link: [./tracks/fix_rrule_object_mapping_20260219/](./tracks/fix_rrule_object_mapping_20260219/)*
+
+---
+
+- [ ] **Track: Fix RRULE UNTIL object conversion error: Invalid UNTIL value: [object Object]**
+  *Link: [./tracks/fix_rrule_until_conversion_20260219/](./tracks/fix_rrule_until_conversion_20260219/)*

conductor/tracks/fix_rrule_until_conversion_20260219/index.md

@@ -0,0 +1,5 @@
+# Track fix_rrule_until_conversion_20260219 Context
+
+- [Specification](./spec.md)
+- [Implementation Plan](./plan.md)
+- [Metadata](./metadata.json)

conductor/tracks/fix_rrule_until_conversion_20260219/metadata.json

@@ -0,0 +1,8 @@
+{
+  "track_id": "fix_rrule_until_conversion_20260219",
+  "type": "bug",
+  "status": "new",
+  "created_at": "2026-02-19T00:00:00Z",
+  "updated_at": "2026-02-19T00:00:00Z",
+  "description": "Fix RRULE UNTIL object conversion error: Invalid UNTIL value: [object Object]"
+}

conductor/tracks/fix_rrule_until_conversion_20260219/plan.md

@@ -0,0 +1,19 @@
+# Implementation Plan - Fix RRULE UNTIL Conversion
+
+## Phase 1: Reproduction
+- [ ] Task: Reproduce `Invalid UNTIL value` error
+    - [ ] Add a test case in `icalendar_test.ts` where `rrule` object has an `until` property as a `Date`.
+    - [ ] Run the test and confirm it fails with `Error: Invalid UNTIL value: [object Object]`.
+- [ ] Task: Conductor - User Manual Verification 'Reproduction' (Protocol in workflow.md)
+
+## Phase 2: Fix Implementation
+- [ ] Task: Implement value formatting logic in `icalendar.ts`
+    - [ ] Update `expandRecurrences` to use a helper for property value conversion.
+    - [ ] Ensure `Date` objects are formatted as `YYYYMMDDTHHMMSSZ`.
+    - [ ] Run the test to confirm it passes.
+- [ ] Task: Conductor - User Manual Verification 'Fix Implementation' (Protocol in workflow.md)
+
+## Phase 3: Verification & Cleanup
+- [ ] Task: Full Regression Check
+    - [ ] Run all tests in `icalendar_test.ts`.
+- [ ] Task: Conductor - User Manual Verification 'Verification & Cleanup' (Protocol in workflow.md)

conductor/tracks/fix_rrule_until_conversion_20260219/spec.md

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+# Specification: Fix RRULE UNTIL Object Conversion
+
+## Overview
+The conversion of RRULE objects to strings fails for nested objects like `UNTIL` dates, resulting in `UNTIL=[object Object]`. This causes the `rrule` library to fail during expansion.
+
+## Functional Requirements
+- **Robust Value Formatting:** Implement `formatRRuleValue` to handle various types of RRULE values:
+    - **Date Objects:** Convert to `YYYYMMDDTHHMMSSZ`.
+    - **Nested Date Objects:** (e.g., `{ date: Date }` from `ts-ics`) Extract and convert.
+    - **Other Types:** Default to string conversion.
+- **Mapping Preservation:** Maintain the existing `RRULE_KEY_MAP` for key translation.
+
+## Implementation Steps
+1.  **Reproduce:** Add test `expandRecurrences - object rrule with until` in `icalendar_test.ts` using a Date object for `until`. Verify it fails with `Invalid UNTIL value`.
+2.  **Fix:** Update `expandRecurrences` in `icalendar.ts` to use a formatting helper for values.
+3.  **Verify:** Confirm the test case passes.
+
+## Acceptance Criteria
+- [ ] Test `expandRecurrences - object rrule with until` passes.
+- [ ] The generated string correctly represents the date (e.g., `UNTIL=20260219T000000Z`).