refactor(lsp): decompose the 687-line LspTask::run God Function

[sinelaw]

What & why

LspTask::run in crates/fresh-editor/src/services/lsp/async_handler.rs was the single largest function in the codebase at 687 lines, inside the largest stable source file (~6.3k lines). Its body was one enormous match cmd { … } whose ~20 request-handling arms were near-identical copy-paste:

LspCommand::Hover { request_id, uri, line, character } => {
    if initialized {
        tracing::info!(...);
        spawn_request!(state, pending, |s, p| s.handle_hover(request_id, uri, line, character, &p).await);
    } else {
        let _ = state.async_tx.send(AsyncMessage::LspHover { request_id, /* empty */ });
    }
}

This is both a God Function and a textbook Copy-Paste Specialist — the repetition buried the parts of run that actually carry logic: the task wiring, the stdout-reader handshake, and the init/notification queue-and-replay loop.

The change

• Moved the ~20 request-dispatch arms (Completion, GotoDefinition, Hover, References, SignatureHelp, CodeActions, InlayHints, all SemanticTokens*, formatting, PluginRequest, …) into a new, documented method LspState::dispatch_request_command.
• run's match now keeps only the commands that genuinely interact with loop-local state — Initialize (drives the draining/replay), the didOpen/didChange/didClose/didSave/workspace-folder notifications (which queue until initialized), CancelRequest, and Shutdown — plus a single catch-all that delegates everything else:

cmd => state.dispatch_request_command(cmd, &pending),

run shrinks from 687 → ~280 lines and reads end-to-end.

Behaviour

No functional change. Each request still gets its own tokio::spawn (the issue #1679 isolation guarantee is preserved verbatim), and the uninitialized fast-path still answers immediately with the same empty/error AsyncMessage. The only thing that moved is where the code lives. No new traits or generics; the one pre-existing local spawn_request! macro simply moved with the arms it serves.

Conflict avoidance

Selected specifically because it is not touched by any of the 55 open PRs (verified by diffing every open PR branch against their merge-base). async_handler.rs does not appear in any open PR's changeset.

Tooling

• cargo build -p fresh-editor — clean.
• cargo fmt — applied.
• cargo clippy --fix --allow-dirty — applied; the file is clippy-clean (remaining crate warnings are pre-existing and in unrelated files). Per request, the test suite was left to CI.

🤖 Generated with Claude Code

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