[InDesign pipeline] Claude Code agent, skill, and documentation for the InDesign-to-React workflow

[PAMulligan]

Sub-issue of #62.

Summary

Ship the InDesign pipeline as a first-class Aurelius workflow: a dedicated Claude Code agent, an InDesign-conversion skill, CLI integration, and end-to-end documentation. This is the user-facing surface that turns the underlying pipeline (#63–#66) into something developers actually use.

Details

Agent

• Add agents/indesign-to-react.md describing the agent's role, allowed tools, and step-by-step procedure (validate input → parse → map tokens → generate → review report → commit).
• Agent reads the generation report and proposes concrete follow-ups (unmapped frames, font fallbacks to confirm, image alt text to add, semantic-tag refinements).
• Agent is non-destructive by default: writes to a feature branch, never to main.

Skill

• Add skills/indesign-conversion/ with a SKILL.md covering: when to use, prerequisites (exported .idml or PDF), expected outputs, and common gotchas (CMYK→sRGB shifts, missing fonts, oversized print images, accessibility gaps).
• Include a worked example using the committed fixture.

CLI integration

• Expose aurelius pipeline indesign <input> [--target next|vite|astro] [--styling tailwind|css-modules] [--output <dir>].
• Honor existing Aurelius config (aurelius.config.ts) for output paths, target framework, and styling mode.
• Emit machine-readable JSON report alongside the human-readable Markdown report.

Documentation

• Add docs/pipelines/indesign.md covering: exporting from InDesign (IDML and PDF), expected output, fidelity expectations, accessibility checklist, troubleshooting.
• Update README.md Pipelines section to list InDesign alongside Figma and Canva.
• Update top-level table of contents and the v2.0.0 release notes draft.

Acceptance Criteria

• agents/indesign-to-react.md exists, follows the same shape as other Aurelius agents, and is referenced from the agents index.
• skills/indesign-conversion/SKILL.md exists with a runnable example.
• aurelius pipeline indesign --help prints documented usage.
• docs/pipelines/indesign.md is published and linked from the main docs index.
• README's Pipelines section lists InDesign.
• End-to-end smoke test in CI runs the agent against the committed fixture and asserts the generated React project builds and passes Storybook smoke tests.

Dependencies

• [InDesign pipeline] IDML parser and intermediate representation #63, [InDesign pipeline] PDF ingestion as primary input (designer-to-developer PDF handoff) #64, [InDesign pipeline] Style and design-token mapper (paragraph/character styles + swatches → tokens + Tailwind preset) #65, [InDesign pipeline] React component generator (TSX output, Tailwind/CSS Modules, Storybook stories) #66 (the agent orchestrates these)

Notes

This sub-issue is the "closes" candidate for the epic — when this ships, #62 can be closed.