[H-6 / Phase 3] [MEDIUM] Zod-parse checkpoint and intake-context deserialization

[matthewod11-stack]

Full spec: docs/hardening-roadmap-2026-04-16.md#h-6

Description

Two places cast JSON directly to typed objects after minimal validation: intake-context.ts:110 casts after only checking conversationHistory is an array; checkpoint.ts likely similar. A corrupted or version-drifted file passes the check then fails cryptically deeper in a phase.

Current State

• packages/intake/src/intake-context.ts:110 uses return parsed as unknown as IntakeContext.
• packages/core/src/checkpoint.ts — needs audit.

Suggested Fix

• Define IntakeContextSchema in packages/intake/src/schemas.ts.
• Replace deserializeContext body with IntakeContextSchema.parse(JSON.parse(json)).
• Define CheckpointSchema in @sourcerer/core; use it in loadCheckpoint.
• Add version: 1 field to checkpoint file; reject mismatched versions with clear upgrade message.

Verification

• pnpm build passes
• pnpm test passes
• pnpm typecheck clean
• Loading malformed checkpoint → specific path error (not cannot read property X of undefined)
• Loading v0 checkpoint → clear "incompatible checkpoint version" error

Automation Hints

scope: packages/intake/src, packages/core/src/checkpoint.ts
do-not-touch: adapters, output
approach: add-validation
risk: low
max-files-changed: 5
blocked-by: #9
bail-if: intake tests fail

Priority

Medium