Restructure README for impact and fix broken doc links (#1151)

* Restructure README: lead with impact, add Why MFC, fix broken links

- Add tagline and hero blockquote (Gordon Bell, 200T grid points, exascale)
- Promote shock-droplet image to hero position
- Add "Why MFC?" section with 6 key differentiators
- Streamline "Try MFC" with direct Codespace link and first-simulation command
- Remove redundant Getting Started section (Codespaces detail, macOS from-source)
- Deduplicate citation block and star CTA (each appeared twice)
- Move star history chart to bottom
- Fix 3 broken doc links: md_examples, md_running, md_getting-started

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

* Link airfoil example to specific directory

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

* Fix case of 3D_shockdroplet directory in README

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

* Update docs landing page: add Gordon Bell mention, OG tags, and new scaling plot

Add 2025 Gordon Bell Prize Finalist tagline to hero section, OpenGraph
and Twitter Card meta tags for link sharing, GitHub stars badge, updated
SEO meta description, and replace Frontier+Summit scaling plots with a
single three-machine weak scaling figure (El Capitan, Frontier, Alps).
Fix LLNL typo and add El Capitan to compute resources footer.

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

* Add alt text to badge images and fix list indentation

Add alt attributes to all badge <img> tags for accessibility (MD045).
Normalize GPU scaling sub-list indentation from mixed tabs/spaces to
consistent 4-space indent.

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

* Fix og:image to use existing banner.png asset

logo2.png does not exist in docs/res/, causing broken social previews.
Use banner.png which is a known-good asset.

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

* Update README with GitHub assets link

Added a link to GitHub assets in the README.

* Replace static hero image with simulation video

Remove the static shockdrop.png in favor of the embedded shedding
water droplet simulation video, which auto-plays and loops on GitHub.

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

* Replace outdated link with new GitHub asset link

Updated link to the largest known public CFD simulation.

* Clean up whitespace around hero simulation video

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

* Center hero video and add autoplay/loop attributes

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

* Update weak scaling docs with combined El Capitan/Frontier/Alps plot

Replace per-system Frontier SVG with new combined GPU weak scaling
PNG covering El Capitan (MI300A), Frontier (MI250X), and Alps (GH200).
Mark Summit-era sections as historical. Fix typos.

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

* Fix video centering and add playback controls fallback

Use <div> instead of <p> for proper centering of video element.
Add controls attribute as fallback when autoplay is blocked.

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

* Replace Frontier-only scaling plot and remove dead Discussions badge

Update "Is this really exascale?" with combined El Capitan/Frontier/Alps
weak scaling plot. Remove Discussions badge since Discussions is disabled.

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

* Add dark-mode scaling plot with automatic theme switching

Generate inverted-grayscale dark variant of weak scaling plot while
preserving colored data points. Use <picture> element for automatic
light/dark mode switching, matching the star history chart pattern.

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

* Use dark-mode scaling plot in docs performance page

The Doxygen docs site uses a dark theme, so the dark variant of the
weak scaling plot matches better.

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

* Clean up README: fix init->new, remove duplicate run instructions

Fix outdated 'init' subcommand references to 'new' in the Toolchain
table and tab completion note. Remove duplicate shock-droplet run
command and visualization text already covered in Try MFC section.

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson