feat(portals): find the same movie in your other playlists

A movie that exists in several imported Xtream playlists now shows a
"Sources N" chip on its detail page and in the player. Switching playlist
mid-film keeps the timecode, a preferred source can be pinned per movie, and
a failed stream offers the alternatives instead of a dead end.

The governing rule is that a guess is never presented as a fact. Every
metadata value carries where it came from — `api` (the provider said so),
`parsed` (inferred from the title) or `probe` (we contacted the stream).
Facts render as plain tags, guesses are prefixed `~` in a warning colour, and
an unknown value renders no tag at all plus a "check" affordance. Ranking and
failover read through `factualOnly()`, so a filename claiming 4K is
structurally unable to outrank a source that was actually reached. A probe
that could not complete reports "unknown", never "unavailable".

Scope is deliberately narrow: Xtream to Xtream, movies only, Electron only.
Stalker never reaches the `content` table and M3U is a JSON blob whose search
forces live content; both are additive later, since the candidate type
already carries all three portal kinds. In the PWA every entry point is gated
off and the chip renders nothing.

Auto-failover is opt-in and off by default. Each source is tried at most once
per session, so it terminates structurally, and the switch is never silent —
the toast names the new playlist, offers an undo, and warns that the dub may
differ only when both sides state an audio track as fact.

Notable details:
- Playlist names are routinely the pasted URL, credentials included. They are
  never rendered raw; a short host-only label is derived instead.
- Quality is derived from pixel width, not height: a 2.39:1 1080p master is
  1920x800, and bucketing that by height would publish "720p" as a fact.
- Switching is a single `inlinePlayback.set()` so the player and engine
  survive and re-seek; the carried position is read before the 15s
  persistence throttle so it does not rewind.
- Sources from one playlist collapse into a group, since the same film often
  appears there several times under different stream ids.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.changes/portals-vod-multi-source.md

@@ -0,0 +1,10 @@
+---
+type: feature
+area: portals
+---
+
+Movies that exist in several of your playlists now show a "Sources" chip on the
+detail page. Switch playlist mid-film and playback continues from the same
+timecode, pin a preferred source per movie, and when a stream dies the error
+screen offers the alternatives instead of a dead end. Optional auto-switching is
+off by default.