Daemon: OpenAI-compatible /v1/completions for Zed

Parses Qwen-format FIM prompts (prefix- or suffix-first, optional repo/file headers) back into
prefix/suffix and rebuilds them in the trained layout; mode from the model string (ac:symbols /
ac:simple); files located via workspaceRoots by path or content. extensions/zed/README.md documents
the Zed settings; untested against real Zed traffic yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J39imRDT8L7xYbWzsVWd8A

extensions/zed/README.md

@@ -0,0 +1,32 @@
+# Zed
+
+Zed can't load third-party edit-prediction extensions, but its built-in `open_ai_compatible_api` provider can call
+the daemon's OpenAI-compatible endpoint. The daemon parses Zed's Qwen-format FIM prompt back into prefix/suffix and
+rebuilds it in the layout our models were trained on (suffix-first, repo header, symbols, token healing).
+
+1. Run the daemon standalone (see [daemon/README.md](../../daemon/README.md)). Add your project folders to
+   `"workspaceRoots"` in its config, so symbols mode and the `this.` repair can find the files. Zed may not send
+   the file path; the daemon then locates the file by content.
+2. In Zed's `settings.json`:
+
+```jsonc
+{
+  "edit_predictions": {
+    "provider": "open_ai_compatible_api",
+    "open_ai_compatible_api": {
+      "api_url": "http://127.0.0.1:7071/v1/completions",
+      "model": "ac:symbols",          // the context-mode toggle: "ac:symbols" | "ac:simple"
+      "prompt_format": "qwen"
+    }
+  }
+}
+```
+
+The mode can also be switched with `node daemon/src/acctl.ts mode simple`.
+
+**Status: untested against real Zed traffic.** The parser accepts prefix-first and suffix-first Qwen prompts, with
+or without `<|repo_name|>`/`<|file_sep|>` headers, and is covered by the daemon smoke test with a synthetic request.
+Still to check with a logging proxy:
+- whether Zed sends the file path
+- its prefix/suffix truncation
+- whether it streams and cancels superseded requests