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/init.lua

@@ -0,0 +1,33 @@
+--- heph.nvim — the primary surface for hephaestus (tech-spec §8): an
+--- obsidian.nvim replacement that is a thin client of the local `hephd` over
+--- its unix-socket JSON-RPC. This module is the public entry point.
+
+local config = require("heph.config")
+
+local M = {}
+
+--- The resolved config from the last `setup` (nil before setup).
+M.config = nil
+
+--- Configure the plugin. `opts.socket` overrides the daemon socket path;
+--- `opts.keymaps = false` disables the default keymaps. Idempotent.
+function M.setup(opts)
+  local cfg = vim.tbl_deep_extend("force", config.defaults, opts or {})
+  cfg.socket = config.resolve_socket(cfg.socket)
+  M.config = cfg
+
+  require("heph.rpc").setup(cfg.socket)
+
+  if cfg.autostart then
+    local ok = require("heph.daemon").wait_ready(cfg.socket, 500)
+    if not ok then
+      require("heph.daemon").spawn({ bin = cfg.bin, socket = cfg.socket, db = nil })
+      require("heph.daemon").wait_ready(cfg.socket, 5000)
+    end
+  end
+
+  config.apply_keymaps(cfg)
+  return M
+end
+
+return M