feat: persist exact Week Ahead task times (Closes #1270)

src/main.py

@@ -738,6 +738,7 @@ class WeekPlanDay(BaseModel):
     capacity_minutes: int | None = Field(default=None, ge=15, le=1440)
     estimates: dict[str, int] = Field(default_factory=dict, max_length=5)
     free_windows: list[WeekFreeWindow] | None = Field(default=None, max_length=16)
+    start_times: dict[str, str] = Field(default_factory=dict, max_length=5)
 
 
 class WeekPlanUpdate(BaseModel):

src/today_store.py

@@ -578,6 +578,39 @@ class TodayStore:
                     })
                     previous_end = end
                 plan["free_windows"] = normalized_windows
+            if "start_times" in day:
+                start_times = day["start_times"]
+                if not isinstance(start_times, dict) or len(start_times) > 5:
+                    raise ValueError("task start times must be a bounded object")
+                if not set(start_times).issubset(plan["ids"]):
+                    raise ValueError("task start times must belong to work on the same date")
+                occupied = []
+                for identity in plan["ids"]:
+                    if identity not in start_times:
+                        continue
+                    value = start_times[identity]
+                    if (
+                        not isinstance(value, str) or len(value) != 5 or value[2] != ":"
+                        or not value[:2].isdigit() or not value[3:].isdigit()
+                        or int(value[:2]) > 23 or int(value[3:]) > 59
+                    ):
+                        raise ValueError("task start times must use HH:mm times")
+                    start = int(value[:2]) * 60 + int(value[3:])
+                    minutes = plan["estimates"].get(identity)
+                    if not isinstance(minutes, int) or start + minutes > 1440:
+                        raise ValueError("task start times must fit their estimates within the date")
+                    end = start + minutes
+                    if any(start < other_end and end > other_start for other_start, other_end in occupied):
+                        raise ValueError("task start times must not overlap")
+                    windows = plan.get("free_windows")
+                    if windows and not any(
+                        int(window["start_time"][:2]) * 60 + int(window["start_time"][3:]) <= start
+                        and end <= int(window["end_time"][:2]) * 60 + int(window["end_time"][3:])
+                        for window in windows
+                    ):
+                        raise ValueError("task start times must fit retained free windows")
+                    occupied.append((start, end))
+                plan["start_times"] = {identity: start_times[identity] for identity in plan["ids"] if identity in start_times}
             duplicate_ids = seen_ids.intersection(plan["ids"])
             if duplicate_ids:
                 raise ValueError("work must be assigned to only one Week Ahead date")