perf: fetch commitment history in parallel in RecentActivityFeed (Closes #1396)

[Aycode01]

Summary

Closes #1396

RecentActivityFeed.tsx's loadEvents previously fetched per-commitment history sequentially in a for-loop:

for (const commitment of commitments) {
  // ... await apiGet(`/api/commitments/${commitment.id}/history`) ...
}

Each /api/commitments/{id}/history request had to complete before the next one started. For a user with N active commitments, the feed took roughly N × single-request latency to render (instead of max(latency)), and the loading skeleton stayed visible the entire time.

This PR replaces the sequential loop with Promise.allSettled(commitments.map(...)), which issues all per-commitment history requests concurrently, dropping feed render time from N × latency to max(latency) — the loading skeleton disappears as soon as the slowest single request resolves, not after the sum of all of them.

Behavior preserved

• ✅ Per-commitment try/catch-and-log: each request keeps its own try/catch with console.error logging on failure (unchanged from the original), so one failing commitment never blocks or breaks the rest of the feed.
• ✅ Empty-state semantics: commitments that fail or return no events simply contribute no entries, and commitments that succeed still render — identical to before.
• ✅ Promise.allSettled (per the issue's acceptance criteria) guarantees the aggregate never rejects even if an individual request does, and we flatMap only fulfilled results.

Changes

src/components/dashboard/RecentActivityFeed.tsx

• Rewrote loadEvents to use Promise.allSettled(commitments.map(async (commitment) => { ... })) with the original per-commitment try/catch-and-log preserved inside each mapper.
• The mapper resolves to the commitment's enriched FeedEvent[] (or [] on failure); the outer allSettled result is flattened into a single event list.
• Adjusted the FeedEvent type to an intersection (HistoryEvent & { commitmentId: string }) so discriminated-union narrowing on event.kind still works.
• Removed a redundant role="list" on the <ul> to satisfy jsx-a11y/no-redundant-roles.

src/components/dashboard/RecentActivityFeed.test.tsx (new)

Seven tests covering the feed, including:

• Concurrency test — asserts requests are issued in parallel: it mocks apiGet with never-resolving promises, renders the feed, and verifies all N requests are fired before any promise resolves. A sequential implementation could never pass this test, since the 2nd call would only fire after the 1st resolves.
• Resilience test — one commitment's request rejects (logged via console.error) while the other's succeeds; asserts the successful commitment's events still render.
• Rendering, loading, and empty-state tests.

Restored support files (new against upstream/master)

These files exist in the intended feature but were deleted from the repository by the destructive 1ecce7d2 commit and never restored upstream — they currently 404 on upstream/master:

• src/lib/apiClient.ts
• src/lib/client/apiClient.ts
• src/utils/errorHelpers.ts
• src/components/Skeleton.tsx

⚠️ Important context for reviewers: this PR is not adding new dead code. Upstream useTestNotification.ts already imports apiRequest from @/lib/client/apiClient, a module that does not exist on current upstream/master (verified via the GitHub contents API → 404). Restoring these files repairs a broken import on master. They are also transitive dependencies of RecentActivityFeed.tsx (apiGet ← @/lib/apiClient ← ./client/apiClient ← errorHelpers).

Type-safety fixes applied to the restored files

The restored files predate the repo's stricter tsconfig.json settings, so they were brought up to current standards:

• client/apiClient.ts: optional properties assigned conditionally to satisfy exactOptionalPropertyTypes.
• errorHelpers.ts: normalizeApiError builds its passthrough object with conditional field assignment (exact optional properties) and uses safe registry lookups under noUncheckedIndexedAccess.

Motivation

For a user with N active commitments, the sequential loop renders the feed after the sum of all request latencies. With Promise.allSettled, it renders after the maximum single latency — a linear-to-constant improvement that matters most exactly when a user has many commitments (the loading skeleton stays visible for N× latency today).

Testing

Run locally and passing:

• ✅ npx prettier --check on all 6 files
• ✅ npx eslint on all 6 files (0 errors)
• ✅ npx vitest run src/components/dashboard/RecentActivityFeed.test.tsx — 7/7 tests pass, including the new concurrency + resilience tests
• ✅ npx tsc --noEmit — no errors in any of the changed files

Note: the repo's full typecheck currently reports a pre-existing, unrelated error in tests/components/MyCommitmentsGrid.perf.test.tsx (module MyCommitmentsGridSkeleton missing — same upstream 1ecce7d2 deletion artifact, file absent from upstream/master). It is not caused by this PR and CI's typecheck job is configured with continue-on-error: true.

Checklist

• Sequential fetch replaced with Promise.allSettled(commitments.map(...))
• Per-commitment try/catch-and-log behavior preserved
• Test asserting requests are issued concurrently added
• Formatting, lint, and unit tests pass locally
• No errors introduced in the changed files by the full typecheck

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