[devin-ai-integration]

Summary

Three PostgreSQL-related fixes from a pre-release check.

• DateTime parameters lost their time (PostgreSQL): the pg gem encodes a DateTime as a Date, so DateTime.new(2024, 1, 1, 10, 0, 0, '+02:00') was stored as midnight in timestamp / timestamptz columns. encode_timestamp now converts a DateTime to a local Time, the same way it already handles Time (this matches MySQL). The encoder now also runs for timestamptz params. The RBS still declares ::Time, the type rows return, same as on MySQL. Date params are unchanged: they mean midnight.
• Timeout in a transaction raised the wrong error (Ruby < 3.3 with timeout < 0.4, e.g. Ruby 3.1's bundled 0.2.0): the old Timeout leaves the block with throw. The cancelled query left the transaction in error, and its ensure replaced the throw with PG::InFailedSqlTransaction. The legacy transaction template now skips that raise when the block was left without completing under an old Timeout. The transaction still rolls back and Timeout::Error reaches the caller. This also works for nested transactions (savepoints).
• README note on the repeated DST hour: PostgreSQL timestamp and MySQL DATETIME store local wall-clock time. An instant in the hour that repeats when clocks fall back from daylight saving time reads back as the first of the two.

Tests

• Both new tests fail on main and pass on this branch: test_datetime_parameters_keep_their_instant, and test_transaction_timeout_rolls_back_and_keeps_connection_usable (now with a nested-transaction case), both in tests/end2end_pg.rb.
• CI: a new PostgreSQL E2E variant bundled-timeout on Ruby 3.1. Gemfile.e2e honours E2E_TIMEOUT_GEM=0.2.0 by replacing the generated gem 'timeout', '>= 0.4'. Until now every Ruby 3.1 job ran with timeout >= 0.4, so this path was never exercised.
• Local run on Ruby 3.1 with timeout 0.2.0: 3 failures on main, 0 on this branch (93 runs). Ruby 3.4: 93 runs, 0 failures.
• docs/Coverage.md and docs/Testing.md are updated. examples/pg and the pg golden files are regenerated, and steep_expectations.yml is updated for shifted line numbers (still 71 diagnostics).

Checklist

• examples/ is regenerated (rake sqlc_generate_process) and committed
• Tests added or updated (rake test, and rake end2end_* when the generated code changes)
• The generated code stays RuboCop-clean (rake rubocop) and Steep-clean (rake steep)
• Labelled (bug, enhancement, documentation, or breaking) so the release notes are grouped correctly

Requested by: @doron050

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring