heph.nvim: plug-and-play managed daemon (autostart, self-heal, client/server guardrail)

The plugin now manages its own hephd by default (autostart = true): if nothing
is serving the socket it spawns a local daemon against the default XDG paths,
kills only what it spawned on VimLeavePre, and self-heals — rpc.call retries
once through a respawn hook when the connection drops (the prior owner releases
the DB lock on exit, so a respawn can claim it).

- daemon.ensure() connects to an already-running daemon (any mode) or spawns one
  we own; stop_spawned()/is_managed() track lifecycle.
- A server/client daemon you started is always respected (spawn only when nothing
  serves the socket). autostart = false → connect-only, warns/errors if down,
  and clears the self-heal hook so it fails loudly.
- config: autostart defaults true; new `db` option; $HEPH_SOCKET / $HEPH_DB
  fallbacks isolate a dev Neovim onto a separate daemon + DB.

e2e: managed_daemon_spec covers autostart spawn, self-heal-after-kill, and
connect-only error. 10 specs green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

heph.nvim/lua/heph/config.lua

@@ -3,19 +3,25 @@
 local M = {}
 
 M.defaults = {
-  --- Path to hephd's unix socket. `nil` → resolved to the daemon default.
+  --- Path to hephd's unix socket. `nil` → `$HEPH_SOCKET`, else the daemon default.
   socket = nil,
-  --- Spawn a local hephd if the socket is not ready (off by default in v1).
-  autostart = false,
-  --- hephd binary for autostart.
+  --- DB path for an autostarted local daemon. `nil` → `$HEPH_DB`, else hephd's default.
+  db = nil,
+  --- Plug-and-play: spawn (and manage) a local hephd when none is serving
+  --- `socket`. Set `false` when you run your own daemon (server/client): the
+  --- plugin then connects only, and warns if nothing is reachable.
+  autostart = true,
+  --- hephd binary for autostart (on PATH for an installed heph).
   bin = "hephd",
   --- Set the default `<leader>h*` keymaps. `false` to opt out.
   keymaps = true,
 }
 
---- Resolve the socket path, mirroring hephd's `default_socket_path`:
---- `$XDG_RUNTIME_DIR/heph/hephd.sock`, falling back to the temp dir.
+--- Resolve the socket path: explicit opt, then `$HEPH_SOCKET`, then hephd's
+--- default (`$XDG_RUNTIME_DIR/heph/hephd.sock`, temp-dir fallback). The env knob
+--- lets a dev Neovim target a `mise run dev` daemon without touching real data.
 function M.resolve_socket(opt)
+  opt = (opt and #opt > 0) and opt or vim.env.HEPH_SOCKET
   if opt and #opt > 0 then
     return opt
   end
@@ -24,6 +30,17 @@ function M.resolve_socket(opt)
   return (base:gsub("/+$", "")) .. "/heph/hephd.sock"
 end
 
+--- Resolve the DB path for an autostarted daemon: explicit opt, then `$HEPH_DB`,
+--- else nil (let hephd pick its default). Pairs with `resolve_socket` for dev
+--- isolation.
+function M.resolve_db(opt)
+  opt = (opt and #opt > 0) and opt or vim.env.HEPH_DB
+  if opt and #opt > 0 then
+    return opt
+  end
+  return nil
+end
+
 --- Apply the default keymaps (no-op when `opts.keymaps` is false).
 function M.apply_keymaps(opts)
   if not opts.keymaps then