[ewanc26]

What this changes

Implements the feed-side external-media variants left on #102.

• app.bsky.embed.gallery#view is a separate view shape from images#view (its items use thumbnail). Gallery posts previously drew neither media nor a bracketed marker; they now draw their first four pictures in the same image row, including when the gallery is the media half of a recordWithMedia quote.
• An enriched external#view can carry source.title and readingTime. The link card's footer now names the publication and reading time, falling back to the bare host it showed before. A plain link card is unchanged.
• Both shapes are read through Wolfram's wf_embed_parse_view / wf_embed_parse_external_embed_view rather than a second cJSON reader. That parser takes JSON text, so fill_embed serialises the open embed subtree once per fetched post, and only for gallery or external media. The existing images, video poster/duration and quote paths are untouched.

This supersedes #261, which was stacked on the pre-rebase feat/settings-screen branch and became conflicting once #260 landed. The commit is unchanged; it is now cut from main as the flow requires.

The separate getEmbedExternalView article/livestream payloads are composer-side data, not post-view shapes, and are not part of this change.

Verification

• make -C tests all — 1621 checks, 0 failures (sweep, linkcheck and unit tests), including the new gallery note case.
• make -C tests snapshot — 658 checks, 0 failures. The fixtures carry a gallery post and an external card with readingTime and source.title; the flattened fields are asserted and timeline-gallery / timeline-external frames are written.
• make -j4 with devkitPro — cobalt.wuhb built on the same tree before the rebase.
• python3 tools/check-guide.py and bash tools/check-parity.sh pass.

Host-only and device-build verification. No Wii U or Cemu pass was run; the gallery layout and enriched card are not hardware-verified.

Refs #102. Supersedes #261.

Docs

AGENTS.md, README.md, docs/guide.md, docs/PARITY.md and CHANGELOG.md updated. The parity row remains partial for the separate article/livestream query payloads.

Checklist

• CI is green (CI gate and flow / conventions)
• No secrets, tokens or signing keys in the diff
• Tests added or changed with the behaviour; none skipped, disabled or deleted