Recorded todo reminder developer messages in the session log so JSONL transcripts match model-visible context when reminders are enabled.\n\nFixes #2824
`ToolResultContent` is not exported from `@oh-my-pi/pi-ai`; `ToolResultMessage.content` is `(TextContent | ImageContent)[]`. Test only needs text, so type the content array as `TextContent[]`.
`#checkTodoCompletion` used to append a `<system-reminder>` and then call
`#scheduleAgentContinue`, so a text-only acknowledgement ("paused at your
instruction") triggered another `agent_end` that re-ran the same check and
fired the next reminder — counter ticked 1/3 → 2/3 → 3/3 inside a single user
pause without any user input. The user perceived three back-to-back reminders
appear from nowhere; the agent felt implicit pressure to invent busy-work or
take destructive ops to silence the loop.
Added `#todoReminderAwaitingProgress`: a reminder sets it, any `toolResult`
(real tool-level progress) or a new user prompt clears it, and
`#checkTodoCompletion` stays silent while it is set. Reset alongside
`#todoReminderCount` on user prompts, session reset, handoff, and the no-op
short-circuits in `#checkTodoCompletion` so the field never gets stuck.
Escalation through `todo.reminders.max` still works when the agent makes
tool-level progress between stops — that is the case the cap was designed for.
Regression coverage in `agent-session-todo-reminder-loop.test.ts` drives a
mocked `agent.continue` to mirror the bug-reported model behaviour and pins
the contract: exactly one reminder per user pause when the agent only
acknowledges; re-escalation when the agent actually calls a tool between stops.
Fixes#2590
roboomp