feat(broadcast): add july-1 newsletter (template, assets, font) (#5302)

* feat(broadcast): add july-1 newsletter (template, assets, font)

* fix(broadcast): rasterize email logo + flow icons to PNG for client compatibility

Gmail and Outlook strip inline <svg> and don't reliably render <img src=*.svg>,
so the header wordmark and the four flow-mark icons could render blank/broken.
Swap to hosted PNGs (logo.png + readme-*-mark.png, transparent, hi-res) with
alt text, matching the v0.5/v0.6 broadcast pattern. Remove the unused SVGs.

* improvement(broadcast): rename july-1 assets to semantic names

Drop the vestigial readme-/real- prefixes for the self-contained newsletter
folder: flow marks -> mark-{integrate,context,build,monitor}.png (context now
matches its label), screenshots -> feature-{chat,tables,knowledge,files,scheduled-tasks}.png.

* fix(broadcast): correct stale model name in newsletter copy

Claude Fable 5 was added in #4921 but removed in #5020, so it is no longer in
the model catalog. Replace it with Claude Opus 4.8 (current flagship in
providers/models.ts) so the newsletter doesn't advertise an unavailable model.

Author: waleedlatif1