Render only the interaction types a community actually has (#199)

[realmarcin]

Resolves the network-legend item tracked in #199, and confirms the sibling item there is already done. #199 itself stays open for its two remaining cosmetic items (hero gradient on the UMAP/graph header, filter placement).

The legend showed every interaction type on every page

src/communitymech/templates/community.html emitted a static block of ten legend rows — a Taxon swatch plus all nine interaction types — on every community page, regardless of what that community contained. Across the 300 pages that have a network, only 857 rows were meaningful; the other ~2100 advertised categories the graph did not contain.

distinct types in record	pages	legend rows before → after
1	120	10 → 2
2	108	10 → 3
3	67	10 → 4
4	5	10 → 5

Changes

The nine colours are now declared once, in an interaction_legend list, and drive both the legend markup and the script's interactionColors map. Previously those were two hand-maintained copies of the same palette that could silently drift apart. The legend renders only the types present, in canonical order, and the SVG <desc> (the accessible description) now lists those same types rather than a hard-coded "cross-feeding, mutualism, syntrophy, competition, commensalism" example that was wrong on most pages.

Colour collision fixed. Taxon nodes were filled #3b82f6 — the same hex as MUTUALISM — so a taxon circle and a mutualism rectangle were indistinguishable by colour. Taxa are now neutral slate (#94a3b8, stroke #475569), so every hue in the diagram means an interaction type. Slate reads against both the light and dark themes.

Typeless interactions. The script falls back to grey for an interaction with no interaction_type; the legend now mirrors that with an "Other" swatch instead of omitting it. One record hits this path (SynCom_Sesame_Flavor_Baijiu_Fuqu_13Genus).

Also in #199: the stale template is already gone

The issue asks to delete templates/community.html.j2 as a dead duplicate. That file no longer exists — templates/ now holds only two research Markdown files. The similarly-named src/communitymech/templates/community.html.j2 is a different, live file driving just gen-community-pages via render_community_pages.py:121 and must not be deleted. That checkbox can be ticked as-is.

Verification

• 266 tests pass.
• All 305 pages regenerated with just gen-html; docs/ is committed and served verbatim by the Pages workflow, so the regenerated pages are included here.
• The 5 communities with no interactions correctly render no legend at all.
• docs/browser.html and docs/index.html are byte-identical — the diff is confined to the per-community pages.
• Spot-checked the three interesting cases: single-type (ANME_SRB_Marine_Methane_Seep_Consortium → Taxon + Syntrophy), four-type (SF356_Cellulose_Degrader), and typeless (Taxon + Other).

🤖 Generated with Claude Code

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Review round

Reviewing this PR surfaced four findings, filed as #269–#272. Two are fixed here; two are deliberately left open.

Fixed — #269, the palette was not colorblind-safe. The nine interaction colors had never been held to the bar PR #198 applied to the UMAP. Ten of 55 swatch pairs measured below ΔE 15 under simulated protanopia/deuteranopia, and two failures were serious: COMPETITION #ef4444 and PREDATION #dc2626 were only ΔE 10.7 apart in normal vision, and MUTUALISM/SYNTROPHY collapsed to ΔE 4.1 under deuteranopia — the two most common interaction types after cross-feeding. The palette is now selected for separation instead of picked by eye; the full-set minimum goes from 0.0 to 15.4 with no pair under the floor. Original semantics are kept where possible (cross-feeding green, mutualism blue, syntrophy purple, competition red); predation moves off red and niche partitioning off teal, which is where the collisions were.

Re-picking the taxon and "Other" neutrals turned out to matter: the first candidate plum for PREDATION landed ΔE 6.5 from the grey "Other" swatch — a collision visible only when the neutrals are measured as part of the same set rather than bolted on afterwards.

Fixed — #271, nothing kept the palette in sync with the schema. tests/test_network_palette.py now asserts the palette covers InteractionTypeEnum exactly and holds the ΔE floor. Without it a tenth enum value would render silently grey on every page rather than failing anything. Verified by mutation: restoring the old reds fails four tests, removing a type fails the coverage test.

Left open — #270, interaction type is encoded by color alone. Every interaction is the same rounded rectangle, so color is the only channel. Nine categories is past what color can reliably carry: reaching ΔE ~30 requires an aesthetically extreme set that collapses back to ΔE 5–9 if any single color shifts, and tritanopia still merges two of them. The UMAP already solves this with a redundant symbol scale; the network needs the same. That is a feature, not a rendering fix.

Left open — #272, network-quality.yml is invalid YAML and has failed every run for at least 15 runs, so its audit has never executed. Pre-existing and unrelated. Not fixed here because repairing the parse would activate a dormant job that calls a paid API and writes PR comments.