Taxonomy counts show 0 and architecture overview graph empty after pssg consolidation

[jonathanpopham]

Bug

After the pssg consolidation in 8f1470b (Feb 17), sites generated by arch-docs show:

• 0 for all taxonomy hero stats (Node Types, Languages, Domains, Subdomains, etc.) even though taxonomy entries render correctly via {{range}}
• Empty architecture overview graph on the homepage (#arch-overview-data is "")

Working example (built before consolidation): https://repos.supermodeltools.com/supermodel-api-docs/
Broken example (built after): https://repos.supermodeltools.com/typescript-sdk/

Root Cause

1. Custom len function missing []taxonomy.Entry type

internal/pssg/render/funcs.go introduces a custom length template function with a type switch:

func length(v interface{}) int {
    switch val := v.(type) {
    case []string:
        return len(val)
    case []*entity.Entity:
        return len(val)
    // ... other types
    }
    return 0  // ← falls through for []taxonomy.Entry
}

When templates call {{len .Entries}} on taxonomy data ([]taxonomy.Entry), no case matches and it returns 0. Meanwhile {{range .Entries}} works fine because Go's range uses native reflection.

Fix: Replace the brittle type switch with reflect.ValueOf(v).Len() to handle any slice/map/string generically.

2. ArchData never populated in renderHomepage

Commit 080b1f2 added the ArchData field to HomepageContext and the template references it, but renderHomepage in build.go never sets it. It always renders as "".

Fix: Build domain graph JSON (nodes + links) from the taxonomy data in renderHomepage.

Affected Templates

• index.html — homepage hero stats (all 0), arch overview graph (empty)
• taxonomy_index.html — "0 categories available"
• letter.html — "0 entries starting with X"

Introduced In

• 8f1470b — Consolidate graph2md and pssg into internal packages
• 080b1f2 — Add missing template fields (added ArchData field but never wired it)