test(cbinding): harden C binding coverage 18% to 93% (#447)

* docs: add Q2 2026 roadmap design spec from multi-persona audit

Full-project audit using 5 parallel analytical personas (Performance,
SQL Compatibility, API/DX, Competitive, Community). Synthesizes into
prioritized P0–P3 roadmap covering: HN launch, query fingerprinting,
linter expansion to 30 rules, DML transforms, C binding hardening,
live DB schema introspection, SQL transpilation, CONNECT BY, OTel,
GORM integration, and advisor expansion.

Corresponding GitHub issues: #442–#460

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: add Q2 2026 implementation plans for all roadmap items

12 implementation plans covering all prioritized GitHub issues:

P0 (Critical):
- 2026-03-29-sentry-fixes.md (#434, #437) — fix Sentry noise filters
- 2026-03-29-openssf-scorecard.md (#443) — security scorecard badge

P1 (High Priority):
- 2026-03-29-query-fingerprinting.md (#444) — SQL normalization + SHA-256 fingerprints
- 2026-03-29-linter-expansion.md (#445) — L011-L030 safety/performance/naming rules
- 2026-03-29-dml-transforms.md (#446) — SET clause and RETURNING transforms
- 2026-03-29-cbinding-hardening.md (#447) — C binding coverage + stress tests
- 2026-03-29-advisor-expansion.md (#453) — OPT-009 through OPT-020 advisor rules

P2 (Medium Priority):
- 2026-03-29-sql-parser-additions.md (#450, #454, #455, #456) — DDL formatter, CONNECT BY, SAMPLE, PIVOT/UNPIVOT
- 2026-03-29-schema-introspection.md (#448) — live DB schema introspection (Postgres, MySQL, SQLite)
- 2026-03-29-integrations.md (#451, #452) — OpenTelemetry + GORM sub-modules
- 2026-03-29-sql-transpilation.md (#449) — SQL dialect transpilation API

P3 (Low Priority):
- 2026-03-29-p3-items.md (#458, #459, #460) — CLI watch registration, pool stats, JSON functions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(cbinding): add coverage tests, stress tests, and Python ctypes integration (#447)

Raises pkg/cbinding coverage from 18.1% to 93.3% by adding:
- cbinding_testhelpers.go: CGo wrapper functions enabling Go tests to call
  all 9 exported C functions (gosqlx_parse, validate, format, extract_tables,
  extract_columns, extract_functions, extract_metadata, version, free)
- cbinding_coverage_test.go: functional tests for all 9 exported functions
  with valid SQL, invalid SQL, edge cases (empty, unicode, large, CTE, window),
  all DML statement types, and toJSON helper coverage
- cbinding_stress_test.go: 50 goroutines x 100 iterations concurrent parse,
  concurrent validate/format, all-functions concurrency, large SQL (100-clause
  UNION ALL), unicode SQL, mixed valid/invalid, and version singleton stability
- pkg/cbinding/tests/test_ctypes.py: Python ctypes integration test that skips
  gracefully when the shared library has not been built
- pkg/cbinding/tests/run_tests.sh: script to build the library and run Python tests

All 73 tests pass with -race; zero data races detected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Ajit Pratap Singh <ajitpratapsingh@Ajits-Mac-mini-2655.local>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 3 people