Harden podcast extractor: coerce malformed model output + vitest suite

[chrisschouk]

Summary

Hardens src/ai/extractor.ts, whose real job is turning untrusted model output into structured DigestEntry values. Adds a vitest suite covering every failure mode at that boundary, then fixes the three defects the suite surfaced so malformed output recovers or fails cleanly instead of producing wrong output or throwing.

The suite mocks the ai SDK's generateText and drives extractBatch end-to-end with deterministic response strings — no network, no provider key.

Audit note

The task brief assumed a prior pass had already added src/ai/__tests__/extractor.test.ts (13 cases) and a "test": "vitest" script. On inspection none of that existed — no __tests__ dir, no vitest dependency, no test script. This PR builds the suite from scratch.

What's added

• vitest dev dependency + "test": "vitest run" script, wired into CI (pnpm test runs before pnpm build).
• src/ai/__tests__/extractor.test.ts — 39 cases.
• src/ai/__tests__/fixtures.ts — shared config/episode builders and the eval dataset.
• Extractor hardening — a defensive coercion layer (see below).
• CI fix (pnpm-workspace.yaml) — see below.

Coverage by group

Group	Cases	What it pins
Well-formed output	5	array parsing, field mapping, metadata + processedAt, entry keying, token usage
Recovery	8	```json / bare fences, leading & trailing prose, truncated mid-array, inline fences inside string values, missing-field defaults
Clean failure	7	empty string, non-JSON garbage, no [ bracket, truncated first object, empty array, stray control chars, missing-usage token fallback
Count reconciliation	2	fewer / more extractions than episodes
Malformed-object handling	6	the three fixes below + supporting cases
estimateCost	5	batch/per-episode token math, ollama free branch, ~$ formatting, unknown-provider fallback, growth with volume
Eval dataset	6	realistic episode shapes end-to-end

Eval dataset (3 → 6 episodes)

No real Apple Podcasts transcripts are committed to the repo, so the dataset is synthetic-but-realistic: single-guest interview, solo monologue (no guests), multi-guest panel, low-relevance off-topic episode, a mixed 3-episode batch, and a code-fenced reply. A guard test asserts the dataset can't silently shrink back below 6 cases / 8 episodes.

Extractor hardening — three defects found and fixed

The suite first characterised these (tests pinning the broken behaviour); a follow-up commit fixes each with a defensive coercion layer and inverts the tests to assert the corrected behaviour.

1. Lone JSON object was dropped → now recovered. A single {...} extraction object (a plausible response for a single-episode batch) is wrapped and mapped instead of yielding zero entries. A non-extraction object (e.g. an {"error":...} refusal) still yields nothing.
2. No field-type validation → now coerced. Every field is coerced to its declared type: a wrong-typed guests (string) collapses to [], non-object guest/idea/person elements are dropped, and a non-numeric relevanceScore becomes 0. Bad types can no longer leak into a DigestEntry and crash a downstream .map/.length.
3. null array element crashed → now clean. [null] previously threw an unhandled TypeError; it now maps to a clean empty entry, preserving index alignment with the episode list.

CI fix (pre-existing, unrelated breakage)

CI had failed on every main push for the last 8+ commits, and the first run on this branch failed too — but not because of these tests. pnpm 9.15.9 in the setup-node cache step runs pnpm store path, which rejects a pnpm-workspace.yaml that has no packages: field (ERROR packages field missing or empty). The job dies before pnpm install, so the tests never execute.

Fix: declare a root-only workspace (packages: ["."]). This satisfies pnpm's parser while keeping the single existing lockfile importer, so pnpm install --frozen-lockfile stays green. It deliberately does not add web/, whose @totalaudiopromo/ui file: dependency points outside this repo and would fail a frozen install.

Verification (local)

• pnpm test → 39 passed
• pnpm typecheck → clean
• pnpm build → success
• pnpm install --frozen-lockfile → clean (lockfile unchanged)

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