fix(social-layer): add start_time to event query, type, and ordering

[pastarita]

Summary

The Social Layer Event was modeled and fetched with an end_time but no start_time — the field was absent in both the GraphQL query and the TypeScript types. As a result, the profile event lists (ProfileStats) could never order events chronologically and fell back to raw array order (.slice(-3).reverse()). The omission was silent: the missing field read as undefined and TypeScript couldn't flag it because the type agreed with the bug.

Full write-up and the test plan are included in docs/issues/.

Changes

Fix

• Extract EVENTS_QUERY / PROFILES_QUERY into src/app/api/socialLayer/queries.ts (no next/server import) so they're unit-testable; add start_time to both.
• Add start_time to the Event and ProfileEvent interfaces (src/types/StatsSocialLayer.ts).
• Add pure helpers sortEventsByStartDesc / recentEventsByStart (src/helpers/events.ts) that order by start_time descending and push missing/invalid timestamps last (never crash, never NaN-poison the order).
• Use the helper for both the Events Hosted and Events Attended lists in ProfileStats.tsx, replacing the array-order workaround.

Tests — run with npm test (Node's built-in runner on TS, zero new dependencies, no node_modules required):

• tests/socialLayer.queries.test.ts — query projection (TC-A*)
• tests/events.helper.test.ts — ordering behaviour incl. missing/invalid/empty (TC-C*)
• tests/types.assert.ts — compile-time type contract via tsc --noEmit (TC-B*)
• package.json: add test and test:types scripts
• tsconfig.json: exclude the runtime *.test.ts files from tsc (they use Node's native TS loader, which requires explicit .ts import extensions incompatible with the bundler config). The no-extension types.assert.ts stays type-checked.

Docs

• docs/issues/social-layer-event-missing-start-time.md — identification, investigation trace, root-cause & impact analysis, proposed fixes, evidence index.
• docs/issues/social-layer-event-start-time.test-plan.md — test-criterion set, automation/agentic execution protocol, pass/fail gates, traceability matrix.

Verification

Gate	Command	Result
Unit suite	npm test	✅ 11/11 pass
Type contract	npx tsc --noEmit	✅ changed code clean¹
Lint	npm run lint	✅ warnings only, none in changed files
Build	npm run build	⚠️ not run locally²

¹ One pre-existing, unrelated error remains (src/constants/config.ts → icon.png), untouched by this PR — a standalone-tsc image-types artifact that next build resolves.
² sharp couldn't build native bindings in the dev sandbox; CI/Vercel build is unaffected.

⚠️ One thing to confirm before merge

start_time is the symmetric counterpart to the already-present end_time, and matches the canonical Social Layer events schema. However, the live Hasura endpoint (hasura-graph.fly.dev) was unreachable from the dev environment, so I could not introspect it to confirm the exact column name. If the source column is named differently (e.g. start_at), only the two query strings in queries.ts need to match it. A maintainer with schema access should verify.

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