Fix DAP binary resolution for remote worktrees

[TateWalker]

Problem

get_dap_binary passed raw binary names ("flutter", "dart", "fvm")
as commands without resolving them against the host's PATH. WASM extensions
cannot read $PATH directly, so the debug adapter failed to launch on remote
(SSH) worktrees.

Fix

Resolve binary paths using worktree.which(), which works correctly on both
local and remote worktrees. This is consistent with how language_server_binary
already resolves the dart binary.

Related Issues

• Dart debug adapter get_dap_binary resolves locally instead of on the remote host #93

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[TateWalker]

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[TateWalker]

@MrSubidubi checking to see if anything on this needs changing

[MrSubidubi]

I see the brief description above, but would you mind explaining how this prevents the auto-install and also on the $PATH-part? Does this happen because if we boot the remote server CLI, we do not load the full user path and hence need the which-API which does just that?