docs: PR #473 review fixes + local DESIGN.md adoption record

[cjimti]

Follow-up to #473. Two commits.

Summary

132e0bf — Address PR #473 review findings

Post-merge code review surfaced six issues. All addressed.

• Component class-name leakage. Every homepage component class (.hero__*, .section, .section__*, .flagship*, .terminal*, .stack*, .coda*, .ticker*, .dropcap, .outline) now requires .page--home as an ancestor selector. Without scoping, any inner-page markdown using class="terminal" or class="section" would inherit homepage display styling.
• Footer collision. Renamed .footer (and all __rule, __inner, __col, __label, __text, __links, __mono, __base siblings) to .home-footer. Dropped the dead .page--home + .footer adjacent-sibling selector that never matched in the actual DOM nesting.
• Overlay z-index. Lowered body::before (grain) and body::after (vignette) from z-index: 100 to z-index: 1 so the rail (z 50) and skiplink (z 200) are no longer darkened by the vignette.
• :has() fallback. Added @supports not selector(:has(*)) block so headings containing inline code still render with mono+signal on Firefox <121 and Safari <15.4 (less ideal, but readable).
• setInterval leak under navigation.instant. Wrapped the live UTC clock IIFE with window.__kubefwdClock global guard. Each return to the homepage via instant-nav now reuses the existing handle and refreshes the displayed time without registering a new interval.
• Mermaid theme. Added Material's --md-mermaid-* CSS variables to the slate scheme block and a .md-typeset .mermaid container restyle. Architecture and MCP integration diagrams now render with the txn2 dark palette.

4a14b8f — Add local DESIGN.md adoption record

Thin local sidecar to canonical txn2/www/DESIGN.md and tokens.json. References upstream as the source of truth for tokens, typography, components, and voice. Records only what is project-specific and the MkDocs Material learnings that do not apply to the upstream Hugo site.

Sections:

• What is canonical — table mapping every concern (palette, type scale, components, voice, mermaid) to upstream
• Adoption level — explicit "token alignment" per upstream's downstream contract
• File map — what each touched file owns
• Project-specific components — what is used, what is NOT used (with reason), kubefwd-only additions
• MkDocs Material learnings — 12 numbered, named lessons covering: custom homepage template, Material variable overrides, font: false, scoping discipline, footer rename, technical h3/h4 typography, tabbed-set restyle, Mermaid via CSS vars, setInterval guard, dark-only palette, overlay z-index, what Hugo can do that MkDocs cannot
• Voice and copy — defers to upstream
• Updating — workflow for when upstream changes
• Downstream contract for sister projects — instructions for txeh, mcp-s3, mcp-trino, mcp-datahub, mcp-data-platform to use this file as a template

Files

Path	Change
`DESIGN.md`	new, 243 lines
`docs/overrides/home.html`	footer class rename, clock IIFE guard
`docs/stylesheets/extra.css`	scoping, footer rename, z-index, :has fallback, mermaid vars

Test plan

• `mkdocs build --strict` passes
• Homepage renders the same as before the scoping changes (no visual regression)
• Inner pages with markdown that happens to use `class="terminal"` or `class="section"` no longer inherit homepage styling
• Vignette no longer darkens the rail
• Live UTC clock keeps ticking after several instant-nav round trips back to homepage; only one interval handle in DevTools timers
• `/architecture/` Mermaid diagrams render with dark palette (paper text, ink-3 nodes, mute edges)
• `grep -RE "—|–" docs/ DESIGN.md mkdocs.yml` returns nothing
• `DESIGN.md` is discoverable at the repo root, alongside README and CLAUDE.md