Moved TaskStore and Task reminder state/logic into the built-in Task feature. Task tools share the feature-owned session store; Task feature hooks now record Task tool usage and append TaskReminder via SystemItemAppendHandle. Pod/PodInterceptor no longer own TaskStore/TaskReminderState or special-case Task tool reminder emission. Reminder append accounting was fixed so usage and request-threshold compaction see the post-append context. External review approved. Merge validation passed: cargo test -p pod task_reminder --lib, cargo test -p pod hook --lib, cargo test -p pod --lib, cargo test -p llm-worker --lib, cargo fmt --check, cargo check --workspace --all-targets, ./tickets.sh doctor, git diff --check, nix build .#yoi, ./result/bin/yoi pod --help.
