add runtime traffic metrics, node latency probing, and fast latency probe path

[ksong008]

Summary

This PR adds a focused runtime / latency-observability slice on top of optimize/code-quality-fixes.

Included:

• runtime traffic metrics
• runtime traffic responsiveness improvements
• node latency probing
• a fast latency probe path for dialers
• a small follow-up fix to pass the network index correctly in HTTP latency checks

This PR intentionally excludes unrelated UDP endpoint accounting changes to keep the scope reviewable.

Included commits

• 5a5baea feat(control): add runtime traffic metrics
• 970a694 fix(control): improve runtime traffic responsiveness
• 7ec7952 feat(control): add node latency probing
• 974ccfc fix(dialer): pass network index to http latency checks
• ad1cfec feat(dialer): add fast latency probe path

Main changes

Runtime traffic metrics

• add runtime traffic snapshot support in control/runtime_stats.go
• wire runtime metrics into control-plane reporting
• improve runtime traffic read-path responsiveness

Node latency probing

• add node latency probing support in the control plane
• expose node latency snapshot collection
• connect runtime latency data to dialer probing results

Fast latency probe path

• add component/outbound/dialer/latency_probe.go
• introduce a faster dialer latency probe path
• fix network index propagation for HTTP latency checks

Files touched

• component/outbound/dialer/block.go
• component/outbound/dialer/dialer.go
• component/outbound/dialer/direct.go
• component/outbound/dialer/latency_probe.go
• component/outbound/dialer/register.go
• control/control_plane.go
• control/runtime_stats.go
• control/tcp.go
• control/udp.go

Notes

• this PR is based on optimize/code-quality-fixes
• it is intentionally scoped to runtime traffic and latency observability
• it does not include the separate UDP endpoint count restoration change