chore: scaffold website (Astro 6 + Starlight + Tailwind v4)

Phase A of docs/plans/20260604-adr-0042-website.md. Scaffolds the site
under website/ from the Starlight template; adds Tailwind v4 (via
@tailwindcss/vite) bridged to Starlight with @astrojs/starlight-tailwind
(src/styles/global.css + customCss). Production build is green: static
output, Pagefind search index, sharp image optimization.

Template placeholders (title, example pages, sidebar) are left for
Phase B/D. Reconciles the ADR/plan/index wording from "Astro 5" to
"Astro 6" to match the scaffolded toolchain.

docs/adr/0042-public-website-and-documentation-site.md

@@ -26,7 +26,7 @@ planning + `/runda` pass with the user and are recorded below.
 
 ## Decision
 
-1. **Stack — Astro 5 + Starlight + Tailwind v4.** Astro's content-first,
+1. **Stack — Astro 6 + Starlight + Tailwind v4.** Astro's content-first,
    zero-JS-by-default model with the Starlight docs theme fits a
    marketing-landing-plus-heavy-docs site better than the alternative
    considered, SvelteKit + Tailwind (the usual go-to here). Interactive
@@ -65,7 +65,7 @@ planning + `/runda` pass with the user and are recorded below.
      and the rusqlite **backup-API** undo (ADR-0006) → a SQL dump/restore.
    When taken up, this becomes its own ADR + iteration plan.
 
-4. **Hosting — portable static build; Vercel is the likely target.** Astro 5
+4. **Hosting — portable static build; Vercel is the likely target.** Astro 6
    builds to static HTML/CSS with no adapter, so the output deploys equally
    to Vercel, Cloudflare Pages, Netlify, or GitHub Pages. We avoid coupling
    to any one host. **No CI yet** — the site is tested locally (`pnpm dev` /

docs/adr/README.md

@@ -47,4 +47,4 @@ This directory contains the project's ADRs, recorded per
 - [ADR-0039 — EXPLAIN over advanced-mode SQL queries](0039-explain-over-advanced-sql.md) — **Accepted** (2026-05-27), **implemented 2026-05-30 (issue #7)**, **supersedes ADR-0030 §13 OOS-2**. Lets `explain` wrap the advanced SQL commands (`Select`/`SqlInsert`/`SqlUpdate`/`SqlDelete`, plus `with`/CTE which builds a `Select`) in addition to the DSL `ShowData`/`Update`/`Delete` it already covers (ADR-0028), running `EXPLAIN QUERY PLAN` over the validated SQL text through the existing ADR-0028 span-styled plan tree (advanced mode only; DSL `explain` unchanged in both modes). Implemented via a second `Advanced` `explain` CommandNode (`EXPLAIN_SQL`) registered under the shared `explain` entry word — reusing the established `insert`/`update`/`delete` shared-word dispatch (`decide`: SQL-first / DSL-fallback), so `explain show data …` and DSL-only `--all-rows` still reach the DSL node; rejected a `DynamicSubgrammar` mode-gate (its resolution cache key omits `mode`). `build_explain_sql` slices the inner SQL off the source (excludes `explain`) and reuses the existing SQL builders; `do_explain_plan` runs the carried text verbatim, no params. Advanced `explain update`/`delete` now route through SQL (identical plan, full SQL syntax); DSL-explain tests pinned to simple mode. Reframed OOS-2 as a *deferred* exclusion (per ADR-0000's out-of-scope discipline), not a rejection. OOS (deferred): EXPLAIN of DDL (no query plan exists)
 - [ADR-0040 — A per-command completion marker (✓/✗) replaces the `[ok]` summary line](0040-completion-marker-replaces-ok-summary.md) — **Accepted 2026-05-30 (issue #9)**, amends ADR-0014 / ADR-0028 / ADR-0019 output conventions, builds on ADR-0037's mode-tagged echo. An audit of the whole command surface found the `[ok] <verb> <subject>` summary line duplicates the echo line above it (verb+subject) everywhere; its only unique contribution is the success-vs-error signal (and `explain select` even rendered `[ok] explain` with an empty subject post-ADR-0039). Decision: drop the `[ok]` line and the symmetric `"…" failed:` prefix; the echo line gains a trailing inline **✓** (green, success) / **✗** (red, failure) — `running:` becomes a pending state that resolves to `<input> ✓/✗` on completion (status set via the existing `rfind(Echo)` lookup). Content (row counts, structure, data, plan tree, teaching echo) unchanged. Scoped to the DSL/data/SQL family that has the redundant echo+`[ok]` pair; app-command `[ok]` lines (`rebuild`/`export`/`now editing`) are payload-bearing, have no echo to mark, and stay as-is. `ok.summary` retired; `dsl.failed` reduced to the rendered reason. Broad but mechanical snapshot churn. OOS: app-command `[ok]` lines, the `[WRN]` validity indicator, and the tag colours (issue #10)
 - [ADR-0041 — Copy the output panel to the system clipboard](0041-copy-output-to-clipboard.md) — **Accepted 2026-06-02 (issue #11)**, amends ADR-0003's app-command registry (adds **`copy`** / `copy all` / `copy last`). The friction it removes: filing a bug report meant terminal-selecting the output panel and fighting wrapping/borders. New **app-level command** (sigil-free, both modes): `copy` / `copy all` copy the whole panel; `copy last` copies from the most recent echo line to the end. **Mechanism — OSC 52 *and* native (`arboard`), always both**, because OSC 52 acceptance is undetectable (no terminal ack), so a true "fall back when unsupported" can't be built: emit the OSC 52 escape (no new dep — `base64`+`crossterm`; works over SSH; tmux-passthrough-wrapped via `$TMUX`), then a best-effort native write whose failure is ignored (headless host — OSC 52 carried it); the two carry identical content. **Format — plain text verbatim as rendered** (tags, `✓`/`✗`, box-drawing) joined by `\n`, without viewport padding/wrapping; a drift-lock test pins `OutputLine::plain_text` to `render_output_line`. `arboard` added **`--no-default-features`** (drops the `image` crate; X11-only on Linux — `wayland-data-control` deliberately omitted as it ~doubles the dep tree and OSC 52 covers native-Wayland). Security: write-only, scans clean for arboard's tree (cargo audit / osv-scanner / grype), 1Password-maintained, minimal surface. OOS: Markdown export, selection/range, a keybinding, OSC 52 read, `screen` passthrough
-- [ADR-0042 — Public website and documentation site](0042-public-website-and-documentation-site.md) — **Accepted 2026-06-04**. The first public website: a marketing landing page plus the **canonical** user docs. Stack **Astro 5 + Starlight + Tailwind v4** (chosen over SvelteKit + Tailwind for a docs-heavy + marketing site; interactive bits as Astro islands). Showcase demos are **asciinema** `.cast` recordings (scripted-input driver for paced, re-recordable sessions — *not* `history.log` replay), reused inline in docs. The **in-page WASM playground is deferred** (OOS: deferred) behind a stable `Demo` seam, with the portable-core (`dsl`/`app`/`ui`, in-memory `rusqlite` via `ffi-sqlite-wasm-rs`) vs native-edge (Tokio/worker-thread/`crossterm`/persistence/backup-API) boundary recorded for a future ADR + iteration plan. Portable **static build** (Vercel target, but host-agnostic); **no CI yet**; **monorepo** (`website/`). Docs cover the **full supported feature set** with "planned" callouts for the unshipped minority; two wording rules bind user-facing copy — **no engine name** (continues ADR-0002) and **no "DSL"** ("simple mode" / "advanced mode"). Install docs cover **prebuilt binaries + package managers** (D1–D3 track the release tooling). Plan: `docs/plans/20260604-adr-0042-website.md`
+- [ADR-0042 — Public website and documentation site](0042-public-website-and-documentation-site.md) — **Accepted 2026-06-04**. The first public website: a marketing landing page plus the **canonical** user docs. Stack **Astro 6 + Starlight + Tailwind v4** (chosen over SvelteKit + Tailwind for a docs-heavy + marketing site; interactive bits as Astro islands). Showcase demos are **asciinema** `.cast` recordings (scripted-input driver for paced, re-recordable sessions — *not* `history.log` replay), reused inline in docs. The **in-page WASM playground is deferred** (OOS: deferred) behind a stable `Demo` seam, with the portable-core (`dsl`/`app`/`ui`, in-memory `rusqlite` via `ffi-sqlite-wasm-rs`) vs native-edge (Tokio/worker-thread/`crossterm`/persistence/backup-API) boundary recorded for a future ADR + iteration plan. Portable **static build** (Vercel target, but host-agnostic); **no CI yet**; **monorepo** (`website/`). Docs cover the **full supported feature set** with "planned" callouts for the unshipped minority; two wording rules bind user-facing copy — **no engine name** (continues ADR-0002) and **no "DSL"** ("simple mode" / "advanced mode"). Install docs cover **prebuilt binaries + package managers** (D1–D3 track the release tooling). Plan: `docs/plans/20260604-adr-0042-website.md`