v1.12.0

AI-first release (Mermaid-inspired): make ArchLang maximally discoverable, self-describing and
distributable for AI agents. Default SVG output stays byte-identical throughout; every new output
behavior is opt-in (ADR 0007 discipline).

Added — agent context & diagnostics

• llms-full.txt (generated, drift-tested via npm run gen:llms / scripts/gen-llms-full.ts):
  the full language spec, the SKILL.md agent workflow, a manifest-derived CLI reference and the
  complete diagnostic catalog bundled into one system-prompt-ready document (~40 KB). Ships in the
  npm package; the docs site now serves /llms.txt and /llms-full.txt at its root
  (copied into docs-site/public/ by sync-docs.mjs, per llmstxt.org convention).
• arch context: prints the bundle — one command gives a cold-start agent everything
  (arch spec remains the language-only view).
• diagnosticToJson(source, d) + DiagnosticJson (new src/diagnostic-json.ts, exported):
  the CLI's agent-facing diagnostic projection (line/col from byte spans + catalogued fix) is now
  public API for SDK/playground/LSP consumers. CLI JSON output is byte-identical.

Added — always-visible errors & eval spine

• Opt-in error-card SVG: compile(src, { onError: "svg" }) / --error-svg on
  compile/preview/md — a plan that fails to compile still renders a deterministic,
  self-describing SVG card (severity, code chip, line:col, message, catalogued fix; new
  src/backends/error-svg.ts, exported renderErrorSvg). Errors/diagnostics/exit codes are
  unchanged; without the opt-in, a broken plan still produces no bytes. arch md --error-svg
  renders failing fenced blocks as error cards instead of skipping them. Also exported:
  renderPngFromSvg (raster core extracted from the PNG backend).
• Authorability eval hardened: corpus grown 3 → 18 briefs with hand-verified goldens
  (relational placement, dims auto, against wall, multi-bath topology, open-plan opening,
  accessibility briefs, scripting, an intentional-warning shell, 30–126 m²); offline golden
  regression gate wired into CI (npm run eval:ci, no API key); default live-eval model id
  updated.

Added — distribution

• Docs site: plain ```arch fences in any docs page now render as live, editable
  <ArchLive> widgets (markdown-it fence transform; SSR/no-JS keeps the highlighted block;
  ```arch static opts out). Explicit <ArchLive> usage is untouched.
• GitHub Action .github/actions/arch-render (composite, in-repo): render every fenced
  ```arch block in a repo's Markdown via arch md — inputs files/format/out-dir/
  error-svg/version, with a self-test workflow. With error-svg: true (default) broken blocks
  become error-card images and the job stays green.
• Playground: Copy-for-LLM button (current source + describe() facts + diagnostics with
  fixes + spec pointer as one paste-ready prompt; pure buildLlmPrompt helper) and diagnostics
  now show their catalogued fix inline (full cause/example still behind the disclosure).

Added — accessibility as a language feature

• compile(src, { accessible: true }) / arch compile --accessible: the SVG carries
  <title> (plan name), <desc> (a derived one-sentence caption) and role="img" +
  aria-labelledby. The caption is also exposed as describe().caption (same sentence,
  guaranteed identical). Default output byte-identical without the flag.
• accTitle / accDescr plan-level keywords (the release's one language-surface change):
  explicit accessible metadata overriding the derived title/caption. Duplicate → new
  W_DUP_ACC_METADATA (last wins); misplaced → new E_ACC_PLACEMENT. Grammar/spec/editor
  artifacts regenerated; new examples/accessible.arch; arch fmt prints and preserves both.
  VS Code extension repack required (it bundles the core).