Phase 12 + 13: collocation coach + vocabulary garden

Phase 12 — collocation coach: a third suggestion family for gentle
"natives usually say…" hints on non-native word pairings, reusing the
existing runPass/pendingScope/rail machinery.
- llm/collocation.go (RunCollocation, 25s floor, reuses ParseCheckpoint)
  + collocationSystemPrompt/CollocationMessages (warm, Mandarin gloss,
  defers grammar/spelling to the grammar family)
- migration 0005 rebuilds the suggestions table to extend the type CHECK
  (SQLite can't ALTER a CHECK)
- collocationScope + CollocationLimit + POST /{id}/collocation
- fix: grammarScope was `type != 'voice'` and would wipe the new
  collocation flags; now `type NOT IN ('voice','collocation')`
- frontend: --color-blossom, "Make it sound natural 🌸" pill,
  collocating/runCollocation in useCheckpoint, StatusBar dot

Phase 13 — vocabulary garden: capture looked-up words and surface them
for gentle spaced repetition.
- new internal/vocab package: migration 0006 (vocab_words, SM-2-lite
  columns, doc_id ON DELETE SET NULL, UNIQUE(user_id,word)),
  scheduler.go (Leitner ladder 1/3/7/16/35 then geometric; gentle
  "again", no streak-shaming), handlers (capture-upsert/list/due/
  review/delete, owner-scoped, SQLite-side datetime math)
- auto-capture on word lookup (dictionary-known words only, captures
  the surrounding sentence + doc_id) + 🤍/💚 toggle on WordCard
- GardenPanel: blossom grid (bloom by reps), flashcard review (sentence
  blanked, flip, again/good/easy, recognition↔production), sleepy-kitten
  footer; opened from a global 🌷 header button

Tests: TestCollocationPassCoexists, vocab scheduler + handlers, db CHECK
extended. go build/vet/test + tsc + vite + vitest (51/51) clean;
migration verified against a copy of the live DB; live backend smoke
walked the full vocab lifecycle + the warm-502 collocation path.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

cmd/server/main.go

@@ -20,6 +20,7 @@ import (
 	"gitea.parodia.dev/drwily/petal/internal/llm"
 	"gitea.parodia.dev/drwily/petal/internal/suggestions"
 	"gitea.parodia.dev/drwily/petal/internal/tts"
+	"gitea.parodia.dev/drwily/petal/internal/vocab"
 	"gitea.parodia.dev/drwily/petal/web"
 )
 
@@ -83,6 +84,10 @@ func main() {
 		api.Mount("/word", lex.Routes())
 		api.Mount("/gloss", lex.GlossRoutes())
 
+		// Vocabulary garden: words the writer looks up are captured here and
+		// surfaced for gentle spaced-repetition review.
+		api.Mount("/vocab", vocab.New(database).Routes())
+
 		// Editor image uploads, stored on disk and served back by content hash.
 		imgHandler, err := images.New(cfg.ImageDir)
 		if err != nil {