ipc: address post-review feedback on unified JSON-RPC layer

[Copilot]

Fixes a set of correctness, robustness, and forward-compatibility issues flagged in review of the IPC unification PR.

Changes

server.go

• Naming: rename cw → conn in closeActiveConnections range loop — the map key is net.Conn, not *connWriter
• Doc: drop "asynchronously" from BroadcastEvent godoc — it writes synchronously in the caller's goroutine
• Forward-compat: use protojson.UnmarshalOptions{DiscardUnknown: true} so unknown fields from newer clients don't cause dropped frames

client.go

• Connection-drop safety: add drainReqs(), deferred at the top of readLoop, which closes all outstanding response channels on EOF/scanner error — prevents Call() from blocking indefinitely after a connection drop
• Forward-compat: same DiscardUnknown: true treatment as server side
• Call(): handle closed-channel receive (resp, ok := <-ch) and return "ipc: connection closed" instead of a nil-dereference

Tests (extra_test.go)

• TestBroadcastEvent_Delivery — connects a raw net.Conn, broadcasts an IndexUpdatedEvent, reads and unmarshals the frame end-to-end
• TestBroadcastEvent_NoInterleave — races a broadcast against a blocked handler to assert response and event writes don't corrupt each other
• TestClient_ConnectionDrop — forcibly closes the underlying connection while a Call() is in-flight and asserts it returns an error promptly

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[Copilot]

Pull request overview

Updates the internal IPC unified JSON-RPC framing to be more forward-compatible and robust to connection drops, and adds regression tests around event broadcasting and client disconnect behavior.

Changes:

• Use protojson.UnmarshalOptions{DiscardUnknown: true} on both server and client to tolerate unknown fields from newer peers.
• Ensure in-flight Client.Call() unblocks promptly when the connection drops by draining outstanding request channels on read loop exit.
• Add end-to-end tests for BroadcastEvent delivery/interleaving and for client connection-drop behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
internal/ipc/server.go	Adjusts naming/docs and makes envelope unmarshalling forward-compatible by discarding unknown fields.
internal/ipc/client.go	Adds request-draining on read loop exit, forward-compatible unmarshalling, and safer Call() channel receive handling.
internal/ipc/extra_test.go	Adds new tests covering broadcast delivery/interleaving and client behavior on connection drop.

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