watch --jsonl event stream

[0xLeif]

Part of GOAL.md workstream B.

Newline-delimited JSON events from watch: one JSON object per emitted value (key, value, timestamp from the injected APSClock). Combines with --count/--timeout.

Acceptance criteria

• Each emitted line is a self-contained valid JSON object
• Event shape documented and asserted in tests
• Non-TTY stdout still flushes per event (FileHandle write path)

[0xLeif]

Shipped in PR #2 (aps 0.2.0, merge commit 62198af). Verified in review: gates green, behavior confirmed locally.