chore: bump version to 0.50.9-beta [skip ci]

fix: resolve circular dependency between loops.js and heartbeat.js

docs: add heartbeat feature to CHANGELOG

feat: add /api/loops/heartbeat endpoint to web UI

feat: heartbeat config via loop config dot-notation

chore: bump version to 0.50.7-beta [skip ci]

feat: add loop heartbeat CLI command with formatted output

chore: bump version to 0.50.6-beta [skip ci]

feat: add notification dispatch and deduplication to heartbeat

chore: bump version to 0.50.5-beta [skip ci]

refactor: extract evaluateLoop/buildSummary and add loadHeartbeatConfig exports to heartbeat.js

chore: bump version to 0.50.4-beta [skip ci]

feat: add heartbeat module for Ralph Loop health monitoring

docs: add heartbeat implementation plan (9 tasks, TDD)

docs: add Ralph Loop heartbeat design spec