[codex] Refactor docs district topology

[8Dionysus]

Summary

Refactors the root docs surface into role-named districts so abyss-stack source docs reflect the AbyssOS source/runtime split instead of a flat documentation layer.

Changes

• Move repo-wide docs into docs/routes, docs/runtime, docs/install, docs/operations, docs/profiles, docs/governance, and docs/legacy.
• Add district README files and a decision record for the docs topology.
• Update root route docs, AGENTS guidance, validators, tests, quests, mechanics references, and legacy bridges to the new paths.
• Tighten profile docs so PROFILES remains a contract surface and PROFILE_RECIPES owns operating examples.

Validation

• python scripts/validate_decision_records.py
• python scripts/validate_stack.py
• python scripts/validate_nested_agents.py
• python -m pytest -q
• python scripts/release_check.py
• markdown link scan
• active flat docs path scan outside legacy
• git diff --check && git diff --cached --check