feat(server): auto-find port on Windows with async

[erroris3]

• Remove polling for port when its not found the opencode to randomly assign a free port and return
• Made its all async now its no more UI lag.

BUT i giveup on finding the process cwd on windows so skip the check for that. Checking the parent should be enough (?).

[Copilot]

Pull Request Overview

This PR enhances the server port detection mechanism by adding asynchronous operations and automatic port finding capabilities. The changes eliminate UI lag by replacing synchronous io.popen calls with vim.system, and introduce automatic free port detection when no opencode server is found.

Key changes:

• Converted all system command executions from synchronous to asynchronous using vim.system
• Added automatic free port detection in the range 4096-5096 when no server is found
• Implemented Windows support with PowerShell commands (though CWD checking is skipped on Windows)

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
lua/opencode/config.lua	Updated on_opencode_not_found callback to accept a port parameter and append it to terminal command
lua/opencode/cli/server.lua	Replaced synchronous exec with async exec_async, added Windows-specific server finding logic, implemented free port detection, and converted all port finding operations to async callbacks

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[erroris3]

I have fix all the copilot suggest

[NickvanDyke]

Thanks @erroris3 ! I can check this out later today I think.

Remove polling for port when its not found the opencode to randomly assign a free port and return

I wonder if we should add a special option to opts.port for this, like "random"? I believe this approach won't find external opencodes, so perhaps it should be opt-in (and the default on Windows).

[erroris3]

It nice to have but this PR is already done that automatically

[erroris3]

I found out that test_port need to be in schedule. It should be fixed now