D&D: import Open5e SRD spell lists, make the five casters playable

Rebuilds the cmd/open5e-import CLI (fetch/gen × spells) to vendor
data/open5e/spells.json (319 SRD spells) and generate
dnd_spells_srd_data.go (237 after the level>5 filter). mapClasses unions
the API's incomplete structured spell_lists field with the complete
free-text dnd_class field so all eight casters get spells.

dndSpellRegistry loads buildSRDSpellList() first; the hand-authored
buildSpellList() overlays it (hand wins on ID collision). Playable=true
flipped for Druid/Bard/Sorcerer/Warlock/Paladin, each with a
defaultKnownSpells case. TestDefaultKnownSpellsExistInRegistry now covers
all eight classes.

.gitignore: vendor data/open5e/ while keeping the rest of data/ ignored,
and anchor the open5e-import binary pattern so it stops swallowing the
cmd/open5e-import source dir. NOTICE adds CC-BY-4.0 / SRD attribution.

cmd/open5e-import/main.go

@@ -0,0 +1,141 @@
+// Command open5e-import vendors Open5e SRD data (CC-BY-4.0) into the repo and
+// regenerates the Go data files the plugin compiles against.
+//
+// It is a pull-once / use-many tool — the generated files are committed, so
+// the running bot has no runtime dependency on the Open5e API.
+//
+//	open5e-import fetch spells   # vendor data/open5e/spells.json from the API
+//	open5e-import gen spells     # classify → internal/plugin/dnd_spells_srd_data.go
+//
+// `bestiary` and `equipment` subcommands are planned; the dispatch below is
+// structured to grow into them without reshuffling.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const (
+	spellsAPIBase = "https://api.open5e.com/v1/spells/?document__slug=wotc-srd&limit=50"
+	spellsJSON    = "data/open5e/spells.json"
+	spellsGenGo   = "internal/plugin/dnd_spells_srd_data.go"
+)
+
+func main() {
+	if len(os.Args) < 3 {
+		usage()
+	}
+	verb, noun := os.Args[1], os.Args[2]
+	switch verb {
+	case "fetch":
+		switch noun {
+		case "spells":
+			must(fetchSpells())
+		default:
+			usage()
+		}
+	case "gen":
+		switch noun {
+		case "spells":
+			must(genSpells())
+		default:
+			usage()
+		}
+	default:
+		usage()
+	}
+}
+
+func usage() {
+	fmt.Fprintln(os.Stderr, "usage: open5e-import (fetch|gen) (spells)")
+	os.Exit(2)
+}
+
+func must(err error) {
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "error:", err)
+		os.Exit(1)
+	}
+}
+
+// open5eSpell is the subset of the Open5e v1 spell schema we consume. Unknown
+// fields are ignored; the vendored JSON keeps the full payload.
+type open5eSpell struct {
+	Slug                  string   `json:"slug"`
+	Name                  string   `json:"name"`
+	Desc                  string   `json:"desc"`
+	HigherLevel           string   `json:"higher_level"`
+	Range                 string   `json:"range"`
+	Material              string   `json:"material"`
+	CanBeCastAsRitual     bool     `json:"can_be_cast_as_ritual"`
+	Duration              string   `json:"duration"`
+	RequiresConcentration bool     `json:"requires_concentration"`
+	CastingTime           string   `json:"casting_time"`
+	LevelInt              int      `json:"level_int"`
+	School                string   `json:"school"`
+	// SpellLists is the structured class list, but the SRD dump leaves it
+	// incomplete (no paladin entries at all). DndClass is the free-text
+	// "Druid, Wizard" field and is the more complete source — mapClasses
+	// unions both. Keep both fields vendored.
+	SpellLists []string `json:"spell_lists"`
+	DndClass   string   `json:"dnd_class"`
+}
+
+type spellsPage struct {
+	Next    string        `json:"next"`
+	Results []open5eSpell `json:"results"`
+}
+
+// fetchSpells pages through the SRD spell list and writes the full result set
+// to data/open5e/spells.json, pretty-printed for a reviewable diff.
+func fetchSpells() error {
+	client := &http.Client{Timeout: 30 * time.Second}
+	var all []open5eSpell
+	url := spellsAPIBase
+	for url != "" {
+		fmt.Fprintln(os.Stderr, "GET", url)
+		page, err := getSpellsPage(client, url)
+		if err != nil {
+			return err
+		}
+		all = append(all, page.Results...)
+		url = page.Next
+	}
+	fmt.Fprintf(os.Stderr, "fetched %d spells\n", len(all))
+
+	if err := os.MkdirAll(filepath.Dir(spellsJSON), 0o755); err != nil {
+		return err
+	}
+	out, err := json.MarshalIndent(all, "", "  ")
+	if err != nil {
+		return err
+	}
+	out = append(out, '\n')
+	return os.WriteFile(spellsJSON, out, 0o644)
+}
+
+func getSpellsPage(client *http.Client, url string) (*spellsPage, error) {
+	resp, err := client.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("%s: HTTP %d", url, resp.StatusCode)
+	}
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	var page spellsPage
+	if err := json.Unmarshal(body, &page); err != nil {
+		return nil, err
+	}
+	return &page, nil
+}