Generate and curate first batch of candidate fixtures (litmus-52qn)

Using findings from research + agent generation, create first batch of candidates:

Priority scenarios:

• ripgrep search results (filename, line number, match highlighting)
• bat/cat syntax-highlighted source code
• journalctl/log viewer with severity colors
• neovim/helix editor UI

For each candidate:

• Write setup.sh + command.sh
• Run capture, inspect output
• Evaluate against quality criteria
• Document assessment in REVIEW.md
• Promote good ones, discard or iterate on the rest

Depends on: staging workflow, research

Plan

1. Create setup.sh + command.sh for each candidate: ripgrep, bat, journalctl, neovim-like
2. Test each locally (FIXTURE_WORK_DIR + command.sh)
3. Parse with litmus-capture parse-ansi
4. Fill out REVIEW.md for each
5. Promote good ones to fixtures/

• Create ripgrep candidate
• Create bat candidate
• Create journalctl candidate
• Create editor-ui candidate
• Test and review all
• Promote passing candidates

Summary of Changes

Created 4 fixture candidates, all passing quality criteria:

1. ripgrep-search — rg search results with heading mode (magenta filenames, green line numbers, bold red match highlighting). 13 lines, uses real rg.
2. bat-syntax — Syntax-highlighted Python with bat (extensive color from syntax theme). 24 lines, fills 80x24 exactly.
3. log-viewer — Simulated structured app logs (INFO/WARN/ERROR/DEBUG levels). 19 lines, pure ANSI 16-color, excellent color variety.
4. editor-ui — Simulated text editor UI (neovim/helix style) with syntax-highlighted Rust, line numbers, and reverse-video status bar. 23 lines, pure ANSI.

All 4 promoted to fixtures/ with output.json, REVIEW.md. Embedded in both litmus-web and litmus-cli. README updated.