0.2.0

Changed

• Rewrote the project in Rust as a SQLite loadable extension
  (libsqlitegpt.{dylib,so,dll}), replacing the previous TypeScript CLI.
  gpt() is now invoked from SQL via .load instead of run as a separate
  command-line tool.
• Split the crate into a workspace: sqlitegpt-core holds the logic and
  tests (linked against bundled SQLite), sqlitegpt is the cdylib shim
  exposing sqlite3_sqlitegpt_init.

Added

• Registered gpt() with SQLITE_DIRECTONLY so it cannot be invoked from
  views, triggers, CHECK/DEFAULT clauses, expression/partial indexes, or
  generated columns. Prevents a hostile database file from triggering
  network calls (and API spend) just by being opened.
• NULL input propagation: gpt(NULL) returns NULL without reading env
  vars or contacting OpenAI.
• 60-second global HTTP timeout via a shared ureq agent, so a hung
  request cannot stall a query indefinitely.
• In-process response cache keyed by (model, prompt). Repeating an
  identical prompt within the same SQLite session reuses the prior answer.
  Set SQLITEGPT_NO_CACHE to disable.
• OPENAI_MODEL environment variable to override the default model.
• Test suite covering response parsing, cache behaviour, NULL
  propagation, DIRECTONLY enforcement, and HTTP timeout.