Add Go-based PokeAPI fetch tool

Replaces the Python fetch_pokeapi.py script with a Go tool that crawls
a local PokeAPI instance and writes seed JSON files. Supports caching
and special encounter definitions via JSON config.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tools/fetch-pokeapi/types.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"strconv"
+	"strings"
+)
+
+// NamedRef is a PokeAPI named resource reference (name + URL).
+type NamedRef struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+}
+
+// ID extracts the trailing integer ID from the URL path.
+// e.g. "https://pokeapi.co/api/v2/pokemon/25/" -> 25
+func (r NamedRef) ID() int {
+	s := strings.TrimRight(r.URL, "/")
+	parts := strings.Split(s, "/")
+	id, _ := strconv.Atoi(parts[len(parts)-1])
+	return id
+}
+
+// ---- PokeAPI response structs (only fields we use) ----
+
+type SpeciesListResp struct {
+	Results []NamedRef `json:"results"`
+}
+
+type RegionResp struct {
+	Locations []NamedRef `json:"locations"`
+}
+
+type LocationResp struct {
+	Areas []NamedRef `json:"areas"`
+}
+
+type LocationAreaResp struct {
+	PokemonEncounters []PokemonEncounter `json:"pokemon_encounters"`
+}
+
+type PokemonEncounter struct {
+	Pokemon        NamedRef        `json:"pokemon"`
+	VersionDetails []VersionDetail `json:"version_details"`
+}
+
+type VersionDetail struct {
+	Version          NamedRef          `json:"version"`
+	EncounterDetails []EncounterDetail `json:"encounter_details"`
+}
+
+type EncounterDetail struct {
+	Chance   int      `json:"chance"`
+	Method   NamedRef `json:"method"`
+	MinLevel int      `json:"min_level"`
+	MaxLevel int      `json:"max_level"`
+}
+
+type SpeciesResp struct {
+	ID             int      `json:"id"`
+	Name           string   `json:"name"`
+	EvolutionChain NamedRef `json:"evolution_chain"`
+	Varieties      []struct {
+		IsDefault bool     `json:"is_default"`
+		Pokemon   NamedRef `json:"pokemon"`
+	} `json:"varieties"`
+}
+
+type PokemonResp struct {
+	ID      int      `json:"id"`
+	Name    string   `json:"name"`
+	Species NamedRef `json:"species"`
+	Types   []struct {
+		Slot int `json:"slot"`
+		Type struct {
+			Name string `json:"name"`
+		} `json:"type"`
+	} `json:"types"`
+}
+
+type EvolutionChainResp struct {
+	ID    int       `json:"id"`
+	Chain ChainLink `json:"chain"`
+}
+
+type ChainLink struct {
+	Species          NamedRef          `json:"species"`
+	EvolvesTo        []ChainLink       `json:"evolves_to"`
+	EvolutionDetails []EvolutionDetail `json:"evolution_details"`
+}
+
+type EvolutionDetail struct {
+	Trigger               NamedRef  `json:"trigger"`
+	MinLevel              *int      `json:"min_level"`
+	Item                  *NamedRef `json:"item"`
+	HeldItem              *NamedRef `json:"held_item"`
+	MinHappiness          *int      `json:"min_happiness"`
+	MinAffection          *int      `json:"min_affection"`
+	MinBeauty             *int      `json:"min_beauty"`
+	TimeOfDay             string    `json:"time_of_day"`
+	KnownMove             *NamedRef `json:"known_move"`
+	KnownMoveType         *NamedRef `json:"known_move_type"`
+	Location              *NamedRef `json:"location"`
+	PartySpecies          *NamedRef `json:"party_species"`
+	PartyType             *NamedRef `json:"party_type"`
+	Gender                *int      `json:"gender"`
+	NeedsOverworldRain    bool      `json:"needs_overworld_rain"`
+	TurnUpsideDown        bool      `json:"turn_upside_down"`
+	TradeSpecies          *NamedRef `json:"trade_species"`
+	RelativePhysicalStats *int      `json:"relative_physical_stats"`
+}