v0.4.0

The "actually usable by a stranger" release. pip install e2er
followed by a one-command e2er run "<RQ>" now starts a local server,
submits the paper, and tails the run to terminal — zero database setup,
zero .env editing required to get to a first paper.

Cross-lane — User journey

• Zero-setup default: e2er serve no longer requires Postgres. The
  DB client dispatches to SQLite at ~/.e2er/papers.db by default; set
  DATABASE_URL=postgresql://… to opt into the production stack
  (pgvector + concurrent writes + literature KB).
• e2er run "<RQ>" subcommand: starts uvicorn in the background if
  needed, POSTs /api/papers, tails status to terminal, prints the
  paper's workspace + dashboard URL on completion. ^C is safe — the
  run keeps going.
• README rewrite: leads with the 5-minute quickstart + the BYO-CLI
  cost matrix. Architecture / artifact list moved below.
• GitHub repo description + topics filled in for discoverability.

Lane C — Data

• Raw-data persistence: every data-pulling subcommand
  (yfinance history, yfinance fundamentals, yfinance dividends,
  fred series) gains a --save-to <rel/path>.csv flag. The wrapper
  writes the response rows to workspace/data/<rel/path> so the
  replication package is runnable offline. Skill files updated to
  mandate --save-to on every meaningful extraction. Closes #11.

Internals

• DB-client dispatch: src/db/client.py now routes SQLite vs Postgres
  by URL scheme. Postgres %(name)s parameter style translates to
  SQLite :name on the fly; Postgres ::type casts are stripped.
  Existing call sites need zero changes.
• sql/sqlite/schema.sql ships a SQLite-compatible schema with the
  core tables (papers, events, contributions, llm_usage, data_query_records,
  data_approval_requests). pgvector-dependent tables (literature_files,
  knowledge_chunks) are NOT created — KB feature degrades to "disabled"
  on SQLite, as designed.
• aiosqlite>=0.20.0 added to dependencies.

Tests

• New: tests/data/contract/test_db_dispatch.py — 9 tests pinning the
  parameter translation, cast stripping, and path resolution.