heph.nvim: rip out auto-spawn — connect-only plugin

The daemon is now an OS service (`heph daemon`); the plugin no longer spawns or
supervises one. Removes the managed-daemon machinery entirely.

- delete lua/heph/daemon.lua (spawn/ensure/stop_spawned/self-heal)
- init.lua: connect-only; probe `health` once and guide to `heph daemon start`
- rpc.lua: drop set_respawn + respawn-on-drop; a dropped connection just
  reconnects once (e.g. after `heph daemon restart`), never spawns
- config.lua: drop autostart/bin/db; stable socket fallback (data-dir, matches
  hephd::default_socket_path), keep $HEPH_SOCKET for dev isolation
- tests: spawn/wait_ready move into the e2e harness (test infra); rework
  managed_daemon_spec into a connect-only spec (connect / clean-fail / reconnect)

16 nvim e2e specs pass.

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

heph.nvim/lua/heph/init.lua

@@ -11,48 +11,29 @@ M.config = nil
 
 --- Configure the plugin. `opts.socket` overrides the daemon socket path;
 --- `opts.keymaps = false` disables the default keymaps. Idempotent.
+---
+--- The plugin is **connect-only** — it never spawns or supervises a `hephd`.
+--- Run the daemon as an OS service with `heph daemon start` ([[run-the-daemon]]);
+--- this just connects to it. If nothing is serving the socket, we notify once
+--- with guidance and let later calls retry (a plain reconnect, never a spawn).
 function M.setup(opts)
   local cfg = vim.tbl_deep_extend("force", config.defaults, opts or {})
   cfg.socket = config.resolve_socket(cfg.socket)
-  cfg.db = config.resolve_db(cfg.db)
   M.config = cfg
 
   local rpc = require("heph.rpc")
-  local daemon = require("heph.daemon")
   rpc.setup(cfg.socket)
 
-  if cfg.autostart then
-    -- Plug-and-play: bring up a managed local daemon if none is serving, and
-    -- self-heal a dropped connection on later calls.
-    local ok = pcall(daemon.ensure, {
-      socket = cfg.socket,
-      db = cfg.db,
-      bin = cfg.bin,
-      autostart = true,
-    })
-    if not ok then
-      require("heph.util").notify(
-        "could not start hephd; will retry on first use",
-        vim.log.levels.WARN
-      )
-    end
-    rpc.set_respawn(function()
-      pcall(daemon.ensure, {
-        socket = cfg.socket,
-        db = cfg.db,
-        bin = cfg.bin,
-        autostart = true,
-      })
-    end)
-  else
-    -- Explicit architecture: connect only, never spawn over the user's daemon.
-    rpc.set_respawn(nil)
-    if not daemon.ensure({ socket = cfg.socket, autostart = false }) then
-      require("heph.util").notify(
-        "no hephd reachable at " .. cfg.socket .. " (autostart disabled)",
-        vim.log.levels.WARN
-      )
-    end
+  -- A cheap liveness probe so a missing daemon is reported up front, not as a
+  -- cryptic error on the first command.
+  local ok = pcall(function()
+    rpc.call("health", {})
+  end)
+  if not ok then
+    require("heph.util").notify(
+      "no hephd at " .. cfg.socket .. " — run `heph daemon start`",
+      vim.log.levels.WARN
+    )
   end
 
   config.apply_keymaps(cfg)