added codex structure

.codex/quality.md

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+# Quality rules
+
+Codex MUST write clean, minimal, maintainable code.
+
+## General rules
+
+Codex MUST:
+
+- prefer simple solutions;
+- avoid over-engineering;
+- avoid unnecessary abstractions;
+- avoid introducing dependencies unless justified;
+- keep functions and modules focused;
+- use clear names;
+- write comments in English only when they add value;
+- preserve existing style unless it conflicts with explicit project rules;
+- keep changes scoped to the requested task;
+- avoid broad rewrites unless explicitly requested.
+
+## Pragmatic TDD
+
+Codex MUST use pragmatic TDD:
+
+- bugfix: write or update a test that reproduces the bug before fixing it, when practical;
+- feature: write tests for expected behavior before implementation, when practical;
+- refactor: rely on existing tests and add missing coverage where needed;
+- documentation-only changes: tests may be unnecessary, but Codex must say so explicitly;
+- infrastructure changes: use syntax checks, dry runs, validation commands, or containerized smoke tests when applicable.
+
+## Completion quality gate
+
+Before completing a task, Codex MUST verify:
+
+- tests were run inside Docker;
+- lint/format checks were run if configured;
+- no unrelated changes were introduced;
+- no secrets were introduced;
+- docs and ADRs were updated if needed;
+- the final commit uses Conventional Commits.