fix(widget): surface unmatched task IDs instead of silently no-opping

CompleteNativeTask/UncompleteNativeTask/RescheduleNativeTask ran a plain
UPDATE ... WHERE id = ? and returned whatever error Exec gave back --
which is nil even when 0 rows match, since that's not a SQL error. A
stale or wrong id from the widget looked identical to a real completion:
HTTP 200, nothing changed in the database. Real incident: 1 of 3 widget
completeTask taps silently no-opped this way.

Now checks RowsAffected() and returns ErrNativeTaskNotFound (mirrors the
existing pattern in sqlite.go's ApproveAgentSession/DenyAgentSession).
HandleWidgetComplete and HandleWidgetReschedule surface this as 404
instead of a fake 200, so the widget can tell 'nothing changed' apart
from 'it worked.'

0 files changed, 0 insertions, 0 deletions