feat: redesign docs page

[alexswearingen]

Description

Before:

After:

Reworks the homepage of https://mjolnir.brokk.ai so the council panel explains how a turn actually runs, and finishes bringing the site's chrome in line with the Bifrost docs. The old panel implied Loki sits on the critical path and ended the turn in a COUNCIL / READY node that corresponds to nothing in the product; it also advertised the Council through a fake shell prompt rather than through the agents that can fill each seat. No runtime, CLI, or documentation-content behavior changes — this is the static marketing page only.

Key Changes:

• Hero kicker becomes a MJOLNIR BY BROKK badge matching the Bifrost hero eyebrow (diamond mark, uppercase mono, BROKK linking to brokk.ai), in Mjolnir's violet rather than Bifrost's red.
• Council diagram is now a round trip instead of a fan-out/fan-in: YOU ⇅ THOR ⇅ EITRI with labelled prompt/answer and delegates/returns lanes, and Loki moved off the spine into a dashed observer card fed by checkpoints from both lanes, returning advice to Thor, tagged ASYNC · NEVER BLOCKS. This tracks docs/src/content/docs/council.md: Thor owns the turn, Eitri is a bounded run in a fresh context, Loki is long-lived, read-only, and never blocks. The COUNCIL / READY terminal node is gone.
• Mock mj --worktree prompt and the role status feed are replaced by a seats board: each role row carries a route chip cycling through Claude Code, Codex, OpenCode, Kimi, and pi. Picks are random and coordinated so no agent appears in two seats at once; rotation is skipped under prefers-reduced-motion, and chips are aria-hidden because the SEATS / ANY ACP AGENT header carries the meaning.
• Panel header is reduced to ● COUNCIL (session number and RAGNAROK: STANDBY removed), the panel is scaled up (54rem → 68rem, diagram 37rem → 52rem) to hold its own against the hero type, and its inner 20px grid texture is dropped because it fought the page background grid.
• Earlier on this branch: JetBrains Mono / Rajdhani / Staatliches are loaded, ~30 one-off rem values are replaced by a named type/spacing/tracking scale, the header is rebuilt as an octagon panel without the terminal council tagline, and the role and capability grids gain __inner wrappers so they align with the section rules.

Touch Points:

• docs/src/components/MjolnirHero.astro — hero badge, council diagram, seat board, seat-rotation script.
• docs/src/styles/mjolnir.css — type, spacing, and tracking scale plus the breakpoint contract shared with the two components.
• docs/src/components/MjolnirHeader.astro, docs/src/content/docs/index.mdx,
  docs/astro.config.mjs — header shell, grid wrappers, font preconnect/stylesheet.

Validation:

• npm run build (docs) — 18 pages built, 833 internal links checked, no errors.
• npm run check (astro check) — 0 errors, 0 warnings, 0 hints.
• Rendered the built site headless in Chromium at 1440×2600 and 390×2800: verified the hero badge, the diagram's lane labels and Loki taps, the seat board, and the stacked mobile layout where the observer card drops below the spine.
• Sampled the seat rotation across ~17s of virtual time and confirmed the chips vary and never show the same agent in two seats simultaneously.
• No Rust checks run (cargo test/clippy); the diff is confined to docs/.

[DavidBakerEffendi]

Could you change this button label to Overview instead of VIEW ON GITHUB? I missed that when I initially created the OG image.

[DavidBakerEffendi]

One comment, otherwise looks great