fix(playbook): improve inline code contrast

[edwin-zvs]

Summary

• render completed Playbook inline code with the normal readable theme foreground on the existing inactive-highlight background in all TUI palette variants
• make the web editor use its normal foreground explicitly on the existing accent-tinted inline-code background
• add focused TUI style assertions across six palettes and real-browser style assertions across all web themes
• leave PR feat(playbook): format inline code while editing #1280 token parsing, source serialization, cursor geometry, hidden delimiters, and Backspace/retype editing behavior unchanged

Validation

• cargo test -p construct-cli playbook_inline_code -- --nocapture
• cargo test -p construct-cli playbook_backspace_after_inline_code_reveals_source_editing_form -- --nocapture
• cargo test -p construct-cli playbook_cursor_math_matches_painted_buffer_differential -- --nocapture
• cargo test -p construct-e2e --test playbook_view web_playbook_view_full_parity -- --exact --nocapture
• cargo build
• git diff --check origin/main...HEAD

All passed after rebasing onto current origin/main.

cargo fmt --all -- --check was inspected but reports repository-wide pre-existing formatting drift across many untouched files; no broad formatting rewrite was applied.

Specs

No spec update. This is a presentation bug fix within the accepted inline-code editing rule in spec 0203, not a new reusable semantic.

Reviewer media

A deterministic before/after TUI capture uses the same isolated daemon, Playbook source, viewport, and keystrokes on both sides. Screenshots will be attached in a PR comment.

[edwin-zvs]

Reviewer media

Deterministic TUI comparison using the same isolated daemon, Playbook Markdown, viewport, theme, and keystrokes.

Before — baseline inline-code renderer (base commit); completed spans use the dark active-highlight foreground on the darker inactive background:

After — fixed renderer (PR commit); completed spans use the readable normal foreground while retaining the highlighted background:

Local originals are retained at /tmp/playbook-inline-code-{before,after}.{png,mp4,gif} for this review session.