chore(release): 0.4.0

[lbguilherme]

Version bump for 0.4.0: workspace version, internal dependency requirements and README.

Since 0.3.0:

• Nullability narrowing.
  • The analyzer now proves NOT NULL from several sources:
    • the conditions a value is read under (WHERE / ON / CASE / FILTER facts, outer-join reduction);
    • foreign keys and CHECK constraints, including partition bounds;
    • row guarantees of joins and subqueries;
    • builtins, set-returning functions and aggregates;
    • what INSERT / UPDATE / ON CONFLICT / MERGE write, for RETURNING.
  • Declared constraints are trusted. The exceptions are documented in CLAUDE.md.
• Soundness.
  • A pg_sanity oracle now executes every accepted query over adversarial data and fails when a value inferred NOT NULL comes back NULL. A dedicated review then closed the holes it and the fuzzer found: DML, functions and aggregates, joins and row guarantees, core typing (cast functions in coercions), and condition facts and CHECK reasoning.
• Diagnostics.
  • Errors are positioned where PG reports them, with PG's hints and name suggestions.
  • Migration errors are located in their file.
  • Parameter errors name the parameter.
  • fetch_*_as::<T>() is checked against the query's columns at compile time.
• Literal validation and conformance.
  • Literals are checked by PG's input grammar for many more types.
  • Type modifiers are read as typenameTypeMod does.
  • No-op casts are dropped where PG's equal() compares expressions (GROUP BY, DISTINCT, DISTINCT ON).
• Migrations and CLI.
  • The runner checks drift before applying, creates the tracking table under the lock and runs non-transactional migrations one statement at a time.
  • sslmode is honored as libpq does.
  • Unknown [package.metadata.typedpg] keys are rejected.
• MSRV raised to Rust 1.89.

This is a minor bump because 0.4 rejects or retypes code that built on 0.3. Columns can change between T and Option<T>, in both directions. Configurations with unknown keys and some queries now fail to compile. The MSRV is higher.

cargo publish --workspace --dry-run packages and builds all six crates.