Utterance award + requirement, and branching dialogue seeding

A dialogue line can award an achievement when reached (granted server-side,
validated against the player's current node so it can't be forged) and an
option can require an achievement to be offered (filtered out of the resolved
tree otherwise). authorGraph gains a branching form (utterance key/parent/
terminal) so option trees — not just linear lines — can be seeded. This is
gaps 1 & 2 for the Barricelli Dobby/Glitch-Hunter dialogues; phone dialing
stays stubbed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/index.ts

@@ -508,6 +508,14 @@ app.post('/api/playthroughs/:id/achievements', async (req, res, next) => {
     result.ok ? res.json({ earned: result.earned }) : res.status(result.error === 'Playthrough not found' ? 404 : 400).json({ error: result.error })
   } catch (error) { next(error) }
 })
+// A dialogue line was reached in play — grant its authored achievement (validated
+// server-side against the player's current node, so players can't forge flags).
+app.post('/api/playthroughs/:id/utterances/:uid/reach', async (req, res, next) => {
+  try {
+    const result = await narrative.reachUtterance(String(req.params.id), String(req.params.uid))
+    result.ok ? res.json({ earned: result.earned ?? false }) : res.status(404).json({ error: 'Not found' })
+  } catch (error) { next(error) }
+})
 // Dev teleport: jump the playthrough to an explicit story node. Powers /node/:id.
 app.post('/api/playthroughs/:id/goto', async (req, res, next) => {
   try {