/care refreshes itself when dosing changes: a mode change, a resume or a stop sends an event on /care/events #620

An open /care page now re-renders its Dosing card when dosing changes, without a reload. I ran the doser, dosing, care and terminal tests (46 pass) and the type check. The type check reports other errors in files I didn't touch (for example src/ui/zone-notes.js), none in the files I changed. I did not run the full check.

• Doser.onChange(fn) (src/doser.ts) calls fn after a mode change, a resume, a halt or a successful dose, and returns a function that unsubscribes. A refused dose that changes nothing sends no event.
• Care routes (src/care-routes.ts): /care/events now also listens to the doser, but only for the owner. A guest's stream carries nothing about dosing.
• One event per change: a dose also writes a log entry, which already sent its own event. The stream now merges changes that land in the same tick, so a dose sends one event instead of two. This applies to every change on the stream, not just dosing.
• Test (src/care-dosing.test.ts): an owner stream and a guest stream on the same server. Each of the four changes sends the owner exactly one event. The guest hears only the three log entries, nothing for the mode change, resume or halt.

The "halt" case in the test is a dose attempted on an out-of-range pH reading.

Closes #618

An open /care page now re-renders its Dosing card when dosing changes, without a reload. I ran the doser, dosing, care and terminal tests (46 pass) and the type check. The type check reports other errors in files I didn't touch (for example src/ui/zone-notes.js), none in the files I changed. I did not run the full check.

• Doser.onChange(fn) (src/doser.ts) calls fn after a mode change, a resume, a halt or a successful dose, and returns a function that unsubscribes. A refused dose that changes nothing sends no event.
• Care routes (src/care-routes.ts): /care/events now also listens to the doser, but only for the owner. A guest's stream carries nothing about dosing.
• One event per change: a dose also writes a log entry, which already sent its own event. The stream now merges changes that land in the same tick, so a dose sends one event instead of two. This applies to every change on the stream, not just dosing.
• Test (src/care-dosing.test.ts): an owner stream and a guest stream on the same server. Each of the four changes sends the owner exactly one event. The guest hears only the three log entries, nothing for the mode change, resume or halt.

The "halt" case in the test is a dose attempted on an out-of-range pH reading.