Add peerconn listener registry for inbound connection lifecycle events

[myleshorton]

Summary

Adds a process-wide listener registry for inbound connection lifecycle events under tracker/peerconn. Used by the radiance peer client (Share My Connection) to surface accept/close events to the rest of the application — Flutter globe visualization, future abuse aggregation, metrics that need a stream rather than a snapshot.

Why this and not adapter.ConnectionTracker

sing-box's tracker abstraction would be the obvious fit but lives behind libbox's internal box.Router with no public hook for callers constructing a libbox.BoxService to register a tracker post-creation. Plumbing one through would require sing-box-minimal changes. This is a smaller hook: single global listener, last-writer-wins, nil to clear.

The registry is callable from any lantern-box inbound — samizdat is wired in this commit; TLS-masq, algeneva, water, etc. is a two-line addition (notify on accept, defer notify on close), keeping the hook protocol-agnostic across lantern-box.

Cost when unused

Zero beyond a mutex read per connection. Standalone CLI / VPN-only consumers (cmd_run, the radiance VPN client) pay nothing meaningful.

Test plan

• go test ./tracker/peerconn/... — 4 unit tests covering nil listener, fire on notify, last-writer-wins, nil unregisters
• go test ./protocol/samizdat/... — existing samizdat tests unaffected
• End-to-end: with the matching radiance branch (fisk/peer-connection-events), connection events flow from accept loop → globe (verified locally)

Related

• radiance: getlantern/radiance#TBD (consumes this listener)
• lantern: getlantern/lantern#TBD (Flutter UI subscribes to the FlutterEvent stream this ultimately feeds)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a process-wide listener registry (tracker/peerconn) that surfaces inbound connection accept/close lifecycle events to external consumers (notably the radiance peer client for Share My Connection). Wires the samizdat inbound to notify on accept and (via defer) on close.

Changes:

• New tracker/peerconn package with SetListener/Notify and a single global listener guarded by sync.RWMutex.
• Unit tests covering nil-listener no-op, fire-on-notify, last-writer-wins, and nil-unregisters semantics.
• Samizdat inbound handleConnection calls peerconn.Notify(+1, source) on accept and defers -1 on close.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tracker/peerconn/listener.go	New package defining Listener type, SetListener, and Notify with a global mutex-guarded listener.
tracker/peerconn/listener_test.go	Unit tests for no-op, dispatch, replacement, and unregister semantics.
protocol/samizdat/inbound.go	Notify peerconn on connection accept and close in handleConnection.

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