Enhance server diagnostics, resource limits, and SQL conformance

[ganeshwhere]

This pull request introduces significant improvements to release management, testing infrastructure, documentation, and some targeted code quality and correctness updates. The main themes are: establishing a robust release gating process (both automated and manual), enhancing test registration and conformance reporting, expanding documentation for operational and developer workflows, and making minor code correctness fixes.

Release Management and CI/CD Enhancements

• Introduced a comprehensive release gate workflow (.github/workflows/release-gate.yml) that enforces build, test, integration, and critical issue checks before a release can proceed. This is documented in detail in docs/release_gate.md and supported by a new release sign-off issue template (.github/ISSUE_TEMPLATE/release-signoff.md). [1] [2] [3]
• Refactored the main CI workflow (.github/workflows/ci.yml) to split quality checks, unit tests, and integration tests into separate jobs, added caching, and ensured coverage on both main and staging branches.

Testing Infrastructure and Documentation

• Explicitly registered all integration test files in Cargo.toml to prevent silent skips, and documented the integration target policy in docs/testing.md. [1] [2]
• Added documentation for the SQL conformance suite and its machine-readable compatibility report artifact, improving release and compatibility tracking. [1] [2]

Operational Documentation

• Added detailed docs for config preflight validation (docs/config_preflight.md) and diagnostics bundle generation (docs/diagnostics_bundle.md), describing commands, output, exit codes, and redaction policies for operational readiness. [1] [2]
• Updated the main README.md with testing and release gate instructions for quick reference.

MVCC and Catalog Improvements

• Expanded MVCC documentation to clarify durability modes, commit durability contracts, and crash behavior, reflecting recent improvements in persistent MVCC support. [1] [2] [3]
• Fixed minor correctness and ergonomics issues in the catalog and executor code, including error message improvements and correct key handling. [1] [2] [3] [4] [5] [6]

Dependency Updates

• Added tokio-rustls and rustls-pemfile as new dependencies in preparation for future secure transport features.

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Release Management and CI/CD

• Added a release gate GitHub Actions workflow and supporting documentation to enforce production readiness, including both automated and manual sign-off procedures. (.github/workflows/release-gate.yml, docs/release_gate.md, .github/ISSUE_TEMPLATE/release-signoff.md) [1] [2] [3]
• Refactored CI workflow to split linting, unit tests, and integration tests into separate jobs, improved caching, and expanded branch coverage. (.github/workflows/ci.yml)

Testing Infrastructure

• Explicitly registered all integration test files in Cargo.toml and documented the policy to prevent silent test skips. (Cargo.toml, docs/testing.md) [1] [2]
• Added SQL conformance suite documentation and machine-readable compatibility reporting. (docs/sql_conformance.md, docs/sql_subset.md) [1] [2]

Operational Documentation

• Added documentation for config preflight validation and diagnostics bundle generation, including command usage, output formats, and exit codes. (docs/config_preflight.md, docs/diagnostics_bundle.md) [1] [2]
• Updated README.md with new testing and release gate instructions. (README.md)

Code Quality and Correctness

• Improved MVCC and catalog error handling, clarified documentation on durability, and fixed minor bugs in executor and filter logic. (src/catalog/mod.rs, src/executor/delete.rs, src/executor/filter.rs, docs/mvcc.md) [1] [2] [3] [4] [5] [6] [7] [8] [9]

Dependencies

• Added tokio-rustls and rustls-pemfile to dependencies for future secure transport support. (Cargo.toml)