Recover active watches from current persisted session origins and exact route
keys, reading heartbeat state off-loop in each source's profile. Failed scans
leave watches intact for the poller's next retry. Start the heartbeat poller
even when startup restores no watches.
Slim synthesis of #92660, #98310 and #98313, with earlier restart recovery
prior art from #92594. The integration poller calls restore_heartbeat_watches
on every poll, including empty registries.
Co-authored-by: chelsealong <chelsealong@126.com>
Co-authored-by: liuhao1024 <sunsky.lau@gmail.com>
Co-authored-by: fangliquanflq <fangliquan@qq.com>
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