[1e] Store project summaries for the picker

Part of Phase 1 (#424) of the data layer plan.

InterlinearProjectSummary written on every project write, with lookups by source; the picker and getPt9ImportForSource read summaries.

Done when: the picker response size doesn't depend on analysis size.

Depends on: 1b (#431).

From the plan

Answer	Today	Planned	Freshness	Issue
Project summaries	Reads every project in full	Stored on every project write	Stored	1e

Two things from #431:

Seeded projects need summaries. The perf harness writes saved projects straight into storage from Node (addSavedProject in perf/storage.ts), copying the record shape. Once project writes store a summary, seeded projects need one, or the picker won't list them. Plan: split projectStorage into a Node-safe core and a thin PAPI wrapper here, and have the seeder call the core.
Don't cache summaries across a view close. The dev-core perf run writes storage while the app runs. If summaries are cached in the host, drop or reload them when a view closes.