fix(server): preserve self binding in heartbeat timer disconnect

[yyueniao]

Tasks

• I read CONTRIBUTING.md
• I ensured my changes pass automated checks
• I reviewed and understand the AI-generated code in my changes (if any)

Description

Fixed a bug in Server:connect() where the heartbeat timer callback self.disconnect was passed as a bare function reference, losing the implicit self receiver. When the timer fired, it would attempt to call disconnect() without the correct self context, causing a runtime error.

How to reproduce

1. Open nvim with opencode configured and start a session
2. Mock a server hang by suspending the server process: pkill -STOP opencode
3. Observe the error message — the heartbeat timer callback fails because self is nil
4. Resume the server afterward: pkill -CONT opencode

The fix wraps the callback in a closure to preserve the self binding:

-- Before
vim.schedule_wrap(self.disconnect)

-- After
vim.schedule_wrap(function()
  self:disconnect()
end)

Testing

1. Verify that :checkhealth opencode passes
2. Connect to an opencode server and confirm the heartbeat timer fires without errors
3. Disconnect and reconnect to ensure no regressions in the connect/disconnect flow

Related Issue(s)

Screenshots/Videos

N/A

[Copilot]

Pull request overview

Fixes a Neovim/Lua method-binding bug in Server:connect() where the heartbeat timer callback previously passed self.disconnect as a bare function reference, causing the method to be invoked without the correct self receiver when the timer fired.

Changes:

• Wrap the heartbeat timer disconnect callback in a closure so it calls self:disconnect() with the correct receiver.
• Reformat the uv_timer:start(...) call for readability while applying the fix.

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[nickjvandyke]

Ope thank you! I noticed this error occasionally but presumed it'd be complicated and didn't have time to investigate.