heph.nvim: RPC client + buffer editing + wiki-links + journal (slice 11a)

The primary surface begins (tech-spec §8): a Neovim plugin that is a thin
client of the local hephd over its unix-socket JSON-RPC.

- node.resolve {title} → Node|null (heph-core Store + dispatch): exact,
  owner-scoped, non-tombstoned alias-then-title match — the same mapping that
  materializes wiki links, so follow-link jumps to the node the stored link
  points at (never fuzzy search). Unit + rpc_socket integration tests.
- heph.nvim/: vim.uv unix-socket JSON-RPC client (blocking call via vim.wait,
  id-demuxed, partial-line buffered, luanil so JSON null → Lua nil; isolated
  Sessions for tests). Buffer-backed nodes (heph://node/<id>, acwrite;
  BufReadCmd→node.get / BufWriteCmd→node.update, whole-buffer body round-trips
  exactly through the CRDT). [[wiki-link]] follow on <CR>. Daily journal.
  :Heph command surface + completion.
- Headless e2e (§9): a self-contained busted-style runner (tests/e2e/runner.lua)
  — no external plugins, no network, deterministic CI exit codes. Specs: journal
  round-trip, follow-link (+ unresolved no-op), link-two-docs/backlink.
  `make -C heph.nvim test` builds hephd and runs it.

Docs: heph-nvim reference card, §14 tracker (11a done; 11b/11c/11d queued),
changelog fragment.

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

heph.nvim/lua/heph/daemon.lua

@@ -0,0 +1,58 @@
+--- Locate, spawn, and wait on a `hephd` daemon. Shared by optional autostart
+--- and by the e2e harness (so test readiness uses the same definition the
+--- plugin does).
+
+local uv = vim.uv or vim.loop
+
+local M = {}
+
+--- Spawn a `local`-mode hephd against `opts.db` listening on `opts.socket`.
+--- `opts.bin` defaults to `hephd` on PATH. Returns `{ handle, pid }`.
+function M.spawn(opts)
+  local args = { "--mode", "local" }
+  if opts.db then
+    table.insert(args, "--db")
+    table.insert(args, opts.db)
+  end
+  if opts.socket then
+    table.insert(args, "--socket")
+    table.insert(args, opts.socket)
+  end
+  local handle, pid = uv.spawn(opts.bin or "hephd", {
+    args = args,
+    stdio = { nil, nil, opts.stderr },
+  }, function(code, signal)
+    if opts.on_exit then
+      opts.on_exit(code, signal)
+    end
+  end)
+  if not handle then
+    error("heph: failed to spawn hephd (bin=" .. (opts.bin or "hephd") .. ")")
+  end
+  return { handle = handle, pid = pid }
+end
+
+--- Wait until `socket` both exists and accepts a real RPC (`health`). The
+--- existence check alone races the daemon's bind→accept, so we prove liveness
+--- with a round-trip on a throwaway session. Returns `true`, or `false, reason`.
+function M.wait_ready(socket, timeout)
+  timeout = timeout or 5000
+  if not vim.wait(timeout, function()
+    return uv.fs_stat(socket) ~= nil
+  end, 20) then
+    return false, "socket never appeared: " .. socket
+  end
+  local session = require("heph.rpc").new_session(socket)
+  local ok = vim.wait(timeout, function()
+    return pcall(function()
+      session:call("health", vim.empty_dict(), { timeout = 200 })
+    end)
+  end, 50)
+  session:close()
+  if not ok then
+    return false, "socket present but not accepting rpc: " .. socket
+  end
+  return true
+end
+
+return M