Add product site system generator

[ShivamGupta42]

Summary

• Add product-site architecture, page-family, and section-pattern datasets.
• Add --site-system CLI mode for sitemap, page matrix, evidence gates, and Claude Design prompt packs.
• Update generated skill templates to route product websites and feature/pricing/use-case pages through --site-system.
• Fix generated install script paths for local/global installs and non-skills/ platforms such as Copilot and Kiro.
• Add validation gates for source/package sync, metadata drift, template paths, generated installs, and Python CLI behavior.

Review/Fix Loop

Completed 3 review cycles with zero remaining P0/P1 findings.

• Cycle 1 fixed generated install paths, cache-safe sync validation, and site-system persisted path mismatch.
• Cycle 2 fixed JSON mode with --persist so stdout remains parseable JSON.
• Cycle 3 fresh review found zero P0/P1 findings.

Deferred P2: git diff --check reports trailing whitespace in synced packaged CSV/script asset diffs. This is not fixed in this loop by design.

Validation

• cd cli && bun run test
• Python unit tests: 7 passing
• Sync, metadata, template, generated-install validators passing
• Generated install script paths execute for Claude, Codex, Copilot, and Kiro
• --site-system -f json --persist stdout parses as JSON, with confirmation on stderr