docs(prime): document the schedule action kinds

src/ClaudeDo.Worker/CLAUDE.md

@@ -33,8 +33,8 @@ Worker/
   Hub/          — WorkerHub, HubBroadcaster
   Logging/      — LogRingBuffer (30-min window) + BroadcastLogSink (Serilog → footer + overlay)
   Report/       — ClaudeHistoryReader, WeekReportPromptBuilder, WeekReportService
-  Prime/        — daily prep ("Prime Claude"): PrimeScheduler, PrimeRunner, DailyPrepPrompt,
-                  NextDueCalculator, PrimeScheduleSignal
+  Prime/        — "Prime Claude" schedules: PrimeScheduler, PrimeRunner, PrimePrompts,
+                  DailyPrepPrompt, PrimeScheduleValidation, NextDueCalculator, PrimeScheduleSignal
   Online/       — optional Online Inbox sync (off by default; zero network when disabled)
   Usage/        — OAuth usage monitor, gate, throttle, per-session token reader;
                   TokenTracker/ = the external analytics backend (cost + per-model/per-task breakdown)
@@ -131,7 +131,26 @@ the **session transcript**, not the stream-json result event, as a per-run delta
 [usage-monitoring](../../docs/explore-notes/usage-monitoring.md). `TaskRunner.ContinueAsync` sends
 a follow-up prompt to an existing session via `--resume <session_id>`.
 
-## Daily Prep (Prime Claude)
+## Prime Claude
+
+Every schedule carries a `PrimeActionKind` (`Ping` — the default for new schedules — `FillMyDay`,
+or `Custom`). `PrimeRunner.FireAsync` holds one `SemaphoreSlim` gate for **all** kinds, then
+branches:
+
+| Kind | Prompt | Args | Log + `Prep*` events |
+|---|---|---|---|
+| `Ping` | `PrimePrompts.PingPrompt`, fixed | `--max-turns 1 --strict-mcp-config` (no MCP server loads at all) | none |
+| `FillMyDay` | `DailyPrepPrompt.BuildPrompt` (+ the schedule's prompt as an *addition*) | the two MyDay MCP tools | `daily-prep.log`, truncated per run, + `PrepStarted`/`PrepLine`/`PrepFinished` |
+| `Custom` | the schedule's prompt *verbatim* | `--allowedTools mcp__claudedo` — no Read/Write/Edit/Bash | none |
+
+Ping and Custom deliberately write **no** log and raise **no** `Prep*` events: the prep log
+belongs to the MyDay selection and would otherwise be overwritten with ping noise. All three
+kinds still broadcast `PrimeFired` and update `last_run_at`.
+
+`WorkerHub.RunDailyPrepNow` (the "Plan day" button) pins its synthetic schedule to `FillMyDay` —
+the button means "fill my day" no matter how the schedules are configured.
+`WorkerHub.UpsertPrimeSchedule` runs `PrimeScheduleValidation.Validate` first, so a `Custom`
+schedule can never be saved without a prompt.
 
 **PrimeScheduler** (`BackgroundService`) computes the next due time from `prime_schedules` and
 calls `IPrimeRunner.FireAsync`; manual runs arrive via `WorkerHub.RunDailyPrepNow`. The