M3-v3: Milestone 1 & 3: Path Decoupling, Pacing Governor, and Sovereign Cloud Failover

[skynetcmd]

This PR implements Milestone 1 and Milestone 3 of the Project M3-v3 (Multi-Session Implementation) specification:

Milestone 1: Path Decoupling & Background Governor

• Decouples user configuration and database engines to standalone locations:
  • Configuration Directory: ~/.m3/config\ (configurable via \M3_CONFIG_ROOT\ or \M3_MEMORY_ROOT/config).
  • Database Engine Directory: ~/.m3/engine\ (configurable via \M3_ENGINE_ROOT\ or \M3_MEMORY_ROOT/engine).
• Implements an Adaptive Background Workload Governor that cooperatively paces daemon tasks based on real-time hardware telemetry and active user sessions:
  • Supports user-selectable resource pacing delay thresholds (\M3_GOVERNOR_INITIAL_THRESHOLD\ and \M3_GOVERNOR_LIMIT_THRESHOLD).
  • Interlocks with de-duplication, PG syncs, and cognitive maintenance loops.
• Enforces distributed migration locking (.migration.lock) and cohesion table validations to prevent database drift.
• Adds \sqlglot\ AST SQL injection guards, removing simple regex-based checks.

Milestone 3: Sovereign Cloud Failover & PII Redaction Gating

• Implements Tier 4 Cloud Enclave failover with PII redaction gating at the secure local boundary, ensuring that no raw un-redacted PII is transmitted over HTTP.
• Resolves cloud credentials dynamically using host OS Keyring and wraps it in Keyring D-Bus circuit breakers with a 2-second timeout and 300s open-circuit cooldowns.
• Embeds a cloud enclave circuit breaker in the cascade to prevent thread blocks.
• 100% test coverage passed in \ ests/test_tier4_cloud.py.