feat(sense): feed browser stream text into segment input assembly
browser_*.jsonl per-site page text now loads in the per-segment percepts assembly via format_browser_text, counts as percepts so browser-only segments are not gated as no-input, and renders under its own Browser Content header.
Both stream-guidance surfaces describe a {host}.browser stream via suffix match. This is read-side assembly only; it adds no new domain writes.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>