feat(nvim): live Telescope filter for the [[ link picker (§8.4)

Replace the "guess a query, then filter a frozen result set" flow with a
live fuzzy filter over every node when Telescope is present: type to
narrow `node.list`, <CR> inserts the highlighted node, <C-x> creates a
doc named the current prompt (a miss flows straight into making it). The
search-then-`vim.ui.select` two-step stays as the no-Telescope fallback.

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

heph.nvim/lua/heph/link.lua

@@ -68,11 +68,74 @@ function M.follow()
   require("heph.node").open(node.id)
 end
 
---- Pick a node (by full-text search) and insert a canonical `[[NODEID]]` link at
---- the cursor — the authoring path for wiki-links-by-id (§8.4); a node id is the
---- only thing that ever enters a stored link, so there's no name ambiguity. A
---- "Create" entry mints a new doc named after the query. No-op if cancelled.
-function M.insert()
+-- Insert the labelled form `[[id|Name]]` at the cursor (readable + conceal-ready;
+-- it collapses to the canonical bare `[[id]]` on save, §8.4).
+local function put_link(id, title)
+  vim.api.nvim_put({ "[[" .. id .. "|" .. title .. "]]" }, "c", true, true)
+end
+
+-- Mint a doc named `title` and insert a link to it.
+local function create_and_put(title)
+  if title and #title > 0 then
+    local node = rpc.call("node.create", { kind = "doc", title = title })
+    put_link(node.id, node.title)
+  end
+end
+
+-- Telescope is available and not explicitly disabled (tests force ui.select).
+local function use_telescope()
+  return not vim.g.heph_force_ui_select and pcall(require, "telescope")
+end
+
+-- A live, fuzzy-filtered Telescope picker over every node: type to narrow,
+-- <CR> inserts the highlighted node, <C-x> creates a doc named the current
+-- prompt text (so a miss flows straight into "make it"). Telescope only.
+local function telescope_insert()
+  local pickers = require("telescope.pickers")
+  local finders = require("telescope.finders")
+  local conf = require("telescope.config").values
+  local actions = require("telescope.actions")
+  local action_state = require("telescope.actions.state")
+
+  local nodes = rpc.call("node.list", vim.empty_dict()) or {}
+  pickers
+    .new({}, {
+      prompt_title = "Link to node  (<C-x> = create from prompt)",
+      finder = finders.new_table({
+        results = nodes,
+        entry_maker = function(n)
+          return {
+            value = n,
+            display = n.title .. "  [" .. (n.kind or "node") .. "]",
+            ordinal = n.title,
+          }
+        end,
+      }),
+      sorter = conf.generic_sorter({}),
+      attach_mappings = function(bufnr, map)
+        actions.select_default:replace(function()
+          local entry = action_state.get_selected_entry()
+          actions.close(bufnr)
+          if entry then
+            put_link(entry.value.id, entry.value.title)
+          end
+        end)
+        local create = function()
+          local title = action_state.get_current_line()
+          actions.close(bufnr)
+          create_and_put(title)
+        end
+        map("i", "<C-x>", create)
+        map("n", "<C-x>", create)
+        return true
+      end,
+    })
+    :find()
+end
+
+-- Fallback when Telescope isn't available: prompt a query, search, then pick
+-- from the results (or a "+ Create" entry). `vim.ui.select` can't filter live.
+local function uiselect_insert()
   vim.ui.input({ prompt = "Link to: " }, function(query)
     if not query or query == "" then
       return
@@ -93,21 +156,26 @@ function M.insert()
     }, function(choice)
       if not choice then
         return
-      end
-      local id, title
-      if choice.__create then
-        local node = rpc.call("node.create", { kind = "doc", title = choice.title })
-        id, title = node.id, node.title
+      elseif choice.__create then
+        create_and_put(choice.title)
       else
-        id, title = choice.id, choice.title
+        put_link(choice.id, choice.title)
       end
-      -- Insert the labelled form `[[id|Name]]` (readable + conceal-ready); it
-      -- collapses to the canonical bare `[[id]]` on save (§8.4).
-      vim.api.nvim_put({ "[[" .. id .. "|" .. title .. "]]" }, "c", true, true)
     end)
   end)
 end
 
+--- Insert a canonical `[[NODEID|Name]]` link at the cursor (§8.4) by picking a
+--- node — live-filtered via Telescope when available, else a search-then-select
+--- prompt. A node id is the only thing that ever enters a stored link.
+function M.insert()
+  if use_telescope() then
+    telescope_insert()
+  else
+    uiselect_insert()
+  end
+end
+
 --- Attach the buffer-local follow/insert keymaps and inline-`#hashtag`
 --- highlighting (only on heph:// buffers).
 function M.attach(buf)