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/plugin/heph.lua

@@ -0,0 +1,52 @@
+--- heph.nvim plugin entry: register the `heph://` buffer autocmds and the
+--- `:Heph` command. Loaded once by Neovim from `runtimepath/plugin/`.
+
+if vim.g.loaded_heph then
+  return
+end
+vim.g.loaded_heph = true
+
+local grp = vim.api.nvim_create_augroup("heph", { clear = true })
+
+-- `heph://node/<id>` buffers load and save through the daemon (tech-spec §8).
+vim.api.nvim_create_autocmd("BufReadCmd", {
+  group = grp,
+  pattern = "heph://*",
+  callback = function(ev)
+    local ok, err = pcall(require("heph.node").read, ev.buf, ev.match)
+    if not ok then
+      vim.notify(tostring(err), vim.log.levels.ERROR)
+    end
+  end,
+})
+
+vim.api.nvim_create_autocmd("BufWriteCmd", {
+  group = grp,
+  pattern = "heph://*",
+  callback = function(ev)
+    local ok, err = pcall(require("heph.node").write, ev.buf, ev.match)
+    if not ok then
+      vim.notify(tostring(err), vim.log.levels.ERROR)
+    end
+  end,
+})
+
+-- Release the socket cleanly on exit.
+vim.api.nvim_create_autocmd("VimLeavePre", {
+  group = grp,
+  callback = function()
+    pcall(function()
+      require("heph.rpc").close()
+    end)
+  end,
+})
+
+vim.api.nvim_create_user_command("Heph", function(opts)
+  require("heph.command").run(opts)
+end, {
+  nargs = "*",
+  desc = "hephaestus",
+  complete = function(arglead, cmdline, cursorpos)
+    return require("heph.command").complete(arglead, cmdline, cursorpos)
+  end,
+})