fix: harden OMDb/TVmaze fetchers and series fallback

TVmaze: drop trailing slash from base URL (was producing //shows/), send
season/number as plain ints (TVmaze rejects zero-padding), check HTTP
status before decoding so 404 bodies stop being decoded as episodes, and
fetch /shows/{id} separately for show name + IMDb mapping —
episodebynumber does not honor embed=show despite what the docs imply.

OMDb: check HTTP status, and include a body snippet when Response is
non-True with an empty Error field so rate-limit and HTML failure modes
are diagnosable.

Both: assert that the fields we actually depend on come back non-empty
after decode. Catches silent field rename/removal without making us
fragile to TVmaze adding new optional fields.

main.processFile: split the nometadata fallback by branch. Series uses
Collection (legitimate shows can have no IMDb mapping); movies keep the
IMDBID/Title check.

internal/metadata/metadata.go

@@ -3,8 +3,10 @@ package metadata
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -13,7 +15,7 @@ import (
 
 const (
 	omdbAPIURL   = "https://www.omdbapi.com/"
-	tvmazeAPIURL = "https://api.tvmaze.com/"
+	tvmazeAPIURL = "https://api.tvmaze.com"
 )
 
 var (
@@ -38,11 +40,10 @@ type TVMazeShowResponse struct {
 }
 
 type TVMazeEpisode struct {
-	Name    string             `json:"name"`
-	Season  int                `json:"season"`
-	Number  int                `json:"number"`
-	Airdate string             `json:"airdate"`
-	Show    TVMazeShowResponse `json:"show"`
+	Name    string `json:"name"`
+	Season  int    `json:"season"`
+	Number  int    `json:"number"`
+	Airdate string `json:"airdate"`
 }
 
 type Client struct {
@@ -94,13 +95,29 @@ func (c *Client) FetchMovieMetadata(imdbID string) (*types.Metadata, error) {
 	}
 	defer resp.Body.Close()
 
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 64*1024))
+	if err != nil {
+		return nil, fmt.Errorf("reading OMDb body: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("OMDb HTTP %d: %s", resp.StatusCode, snippet(body))
+	}
+
 	var result OMDbResponse
-	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
-		return nil, fmt.Errorf("decoding OMDb response: %w", err)
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("decoding OMDb response: %w (body: %s)", err, snippet(body))
 	}
 
 	if result.Response != "True" {
-		return nil, fmt.Errorf("OMDb error: %s", result.Error)
+		if result.Error != "" {
+			return nil, fmt.Errorf("OMDb error: %s", result.Error)
+		}
+		return nil, fmt.Errorf("OMDb non-True response: %s", snippet(body))
+	}
+
+	if result.Title == "" || result.IMDBID == "" {
+		return nil, fmt.Errorf("OMDb response missing Title/imdbID (schema drift?): %s", snippet(body))
 	}
 
 	dateReleased := formatDate(result.Year)
@@ -114,39 +131,75 @@ func (c *Client) FetchMovieMetadata(imdbID string) (*types.Metadata, error) {
 }
 
 func (c *Client) FetchSeriesMetadata(tvmazeID, season, episode string) (*types.Metadata, error) {
-	url := fmt.Sprintf("%s/shows/%s/episodebynumber?season=%s&number=%s", tvmazeAPIURL, tvmazeID, season, episode)
-
-	resp, err := c.httpClient.Get(url)
+	seasonNum, err := strconv.Atoi(season)
 	if err != nil {
-		return nil, fmt.Errorf("fetching TVmaze: %w", err)
+		return nil, fmt.Errorf("parsing season %q: %w", season, err)
+	}
+	episodeNum, err := strconv.Atoi(episode)
+	if err != nil {
+		return nil, fmt.Errorf("parsing episode %q: %w", episode, err)
 	}
-	defer resp.Body.Close()
 
+	epURL := fmt.Sprintf("%s/shows/%s/episodebynumber?season=%d&number=%d", tvmazeAPIURL, tvmazeID, seasonNum, episodeNum)
 	var ep TVMazeEpisode
-	if err := json.NewDecoder(resp.Body).Decode(&ep); err != nil {
-		return nil, fmt.Errorf("decoding TVmaze response: %w", err)
+	if err := c.fetchTVMazeJSON(epURL, &ep); err != nil {
+		return nil, fmt.Errorf("TVmaze episode %s S%dE%d: %w", tvmazeID, seasonNum, episodeNum, err)
 	}
 
-	dateReleased := formatDate(ep.Airdate)
+	showURL := fmt.Sprintf("%s/shows/%s", tvmazeAPIURL, tvmazeID)
+	var show TVMazeShowResponse
+	if err := c.fetchTVMazeJSON(showURL, &show); err != nil {
+		return nil, fmt.Errorf("TVmaze show %s: %w", tvmazeID, err)
+	}
 
-	var imdbID string
-	if ep.Show.Extern.IMDB != "" {
-		imdbID = ep.Show.Extern.IMDB
+	if ep.Name == "" || show.Name == "" {
+		return nil, fmt.Errorf("TVmaze response missing episode/show name (schema drift?) for %s S%dE%d", tvmazeID, seasonNum, episodeNum)
 	}
 
 	return &types.Metadata{
 		Title:         ep.Name,
-		Collection:    ep.Show.Name,
+		Collection:    show.Name,
 		Season:        season,
 		Episode:       episode,
-		DateReleased:  dateReleased,
-		IMDBID:        imdbID,
+		DateReleased:  formatDate(ep.Airdate),
+		IMDBID:        show.Extern.IMDB,
 		TVMazeID:      tvmazeID,
 		IsSeries:      true,
 		OriginalMedia: types.MediaTypeBluRay,
 	}, nil
 }
 
+func (c *Client) fetchTVMazeJSON(url string, v interface{}) error {
+	resp, err := c.httpClient.Get(url)
+	if err != nil {
+		return fmt.Errorf("GET: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 256*1024))
+	if err != nil {
+		return fmt.Errorf("read body: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("HTTP %d: %s", resp.StatusCode, snippet(body))
+	}
+
+	if err := json.Unmarshal(body, v); err != nil {
+		return fmt.Errorf("decode: %w (body: %s)", err, snippet(body))
+	}
+	return nil
+}
+
+func snippet(body []byte) string {
+	s := strings.TrimSpace(string(body))
+	const max = 200
+	if len(s) > max {
+		s = s[:max] + "…"
+	}
+	return s
+}
+
 func formatDate(date string) string {
 	if date == "" || date == "N/A" {
 		return ""