Fix embedding-plot click-through (404 on every point)

[realmarcin]

Problem

Both embedding pages (umap.html, graph.html) recomputed each trait's page URL in the browser as CATEGORY_DIR[d.category]/slugify(d.label).html. Two defects:

1. Category case-mismatch (100% breakage): CATEGORY_DIR is keyed UPPERCASE, but the data's category is lowercase and already equals the directory slug — so CATEGORY_DIR[d.category] was always undefined, and every one of the 477 points fell through to a non-existent traits/other/… page. 0/477 resolved.
2. Label ≠ filename (4 traits): trait page filenames are the YAML file stems, which spell digits as words (dicarboxylate_four_hydroxybutyrate_cycle) and use abbreviations (reductive_tca_cycle). No client-side label-slugifier can reproduce those.

Surfaced by a front-end design review against the dataviz/artifact-design skills.

Fix

Stop recomputing slugs client-side. The renderer already builds the authoritative id→page map (page_path), so inject it into the two templates as HREF_BY_ID and have the click handler use HREF_BY_ID[d.id] directly.

Verification

Recomputed every point's click target against files on disk:

• Before: 0/477 resolve (all 404).
• After: 477/477 resolve — including the 4 digit/abbreviation metabolism traits.

Immune to future label/filename drift since the href is now data, not a re-derivation.

Files: scripts/render_trait_pages.py (inject map), src/traitmech/templates/{umap,graph}.html, regenerated pages/{umap,graph}.html.

🤖 Generated with Claude Code

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[realmarcin]

Reviewed the PR's own diff (source templates + renderer; regenerated pages are consistent).

Clean — no issues. The fix is correct:

• render_trait_pages.py injects href_by_id for both plots from the authoritative page_path map ({p["id"]: page_path.get(p["id"], "") for p in ...}), so the href is data, not a client-side re-derivation.
• umap.html/graph.html click handlers now use HREF_BY_ID[d.id] with an if (href) guard (empty-string fallback is falsy → no bad nav). No slug/category recompute reintroduced.
• Data keys and page filenames unchanged; rendered pages/{umap,graph}.html carry the injected map. Verified id→page targets resolve.

(Minor, non-blocking: the now-unused traits_root="traits/" kwarg is still passed to both render calls — harmless leftover.)