feat(eve): memory provider for eve's first-class memory slots (v0.3.0)

[benfrank241]

Summary

Vercel asked us (on X) to migrate @vectorize-io/hindsight-eve to eve's new memory provider contract. This PR does that as v0.3.0.

hindsightMemory() now returns a MemoryProvider for one authored file:

// agent/memory/hindsight.ts
export default defineMemory({
  description: "Long-term memory about the current user.",
  provider: hindsightMemory(),
  scope: byPrincipal,
});

What the contract fixes vs. the v0.2 hooks/instructions approach:

• Recall runs on the live user message (ctx.turn.input) — v0.2 had to use a fixed broad query because eve's instruction resolver couldn't see it.
• One bank per locked scope (bankId = scope.key) — tenants are isolated as eve requires. A string bankId / HINDSIGHT_BANK_ID still pins a shared bank for single-user agents; a resolver names banks yourself.
• Each turn's recall is one message with a stable id, so it supersedes the previous block instead of accumulating in history (incl. after compaction).
• Captures use eve's operationId as document_id, so a replay replaces rather than duplicates.
• <slot>__reflect tool exposed by default (tools: false to opt out).
• A failed recall reports via onError and never fails the turn; recall on a not-yet-created bank (404) reads as empty.

The v0.2 entrypoints stay for one release as hindsightAutoRecall() / hindsightRetainHook() (deprecated). Dev dep → eve 0.66.2, peer → >=0.45.1. Docs page, README and gallery blurb updated.

Upstream regression found while verifying

eve 0.51.0+ never invokes capture["turn.completed"] for any provider — vercel/eve#2690 dropped the history argument from emitTurnEpilogue. Tracked in vercel/eve#3223 (p0), fix pending in vercel/eve#3465; I added a 0.66.2 confirmation there. README/docs carry a "Known issue" section with the interim (pin eve@0.50.0, or keep the deprecated retain hook alongside the provider).

Test plan

• 59 unit tests (vitest), typecheck, tsup build, lockfile gate
• Provider tests drive eve-shaped MemoryTurnStartedContext / MemoryTurnCompletedContext / MemoryToolsContext against a mocked fetch
• Live e2e against Hindsight Cloud with a scaffolded eve agent (eve dev --no-ui, gpt-4.1): on eve 0.49.1, session 1 "use Python, full type hints, no comments" → captured; fresh session "Write me a throttle function." → typed, comment-free Python, "as per your preferences", zero tool calls. On 0.66.2 recall works and capture never fires (the upstream bug above).
• /code-review — only failure is eslint for the control plane, which has no node_modules in the fresh worktree and isn't touched here

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