feat: add Harness Inventory page

A categorised inventory of error-correction layers for agentic coding,
the second lever of Eichhorst's Principle (after Semantic Anchors as
the signal lever).

Adds a new public page at /harness-inventory:
- Six axes per check layer (What/How/When/Closed-loop/Definition/Cost)
- Definition marker axis (green extrinsic / yellow hybrid / red intrinsic)
- Nine thematic categories (build, tests, security, architecture, data,
  UX/a11y/i18n, operations, formal, docs) with per-row markers
- Orthogonal detection-mode axis (static/dynamic/symbolic/empirical/
  property-based/adversarial/statistical/human/LLM)
- 'What the Harness Does Not Catch' section: spec-, code-, UX-,
  and strategy-level gaps plus language-specific limits
- Risk-tiered dosing (Tier 1-4)
- Cross-links to spec-driven-development, brownfield, socratic-recovery-skill

Implementation:
- docs/harness-inventory.adoc -- AsciiDoc source
- scripts/render-docs.js -- include in HTML build
- scripts/prerender-routes.js -- SEO/prerender route entry
- scripts/generate-sitemap.js -- sitemap entry
- website/src/main.js -- SPA route handler and renderer
- website/src/utils/router.js -- page title
- website/public/sitemap.xml -- regenerated sitemap

Co-Authored-By: Claude Opus 4.7 <noreply\@anthropic.com>

Author: raifdmueller