refactor(supervisor): split progression engine gate checks into modules

[xsovad06]

Objective

Extract 13 gate checks from progression.py (1275 lines) into individual modules under sova/supervisor/gates/, improving testability and readability.

Findings

[P2] progression.py god file (1275 LOC)

• Location: sova/supervisor/progression.py
• Issue: Mixes 13 gate checks, dependency graph interaction, PR state evaluation, and spawn orchestration in one file. Hard to test individual gates in isolation.
• Recommendation: Create sova/supervisor/gates/ with one module per gate (e.g., rate_limit.py, memory_pressure.py, dependency.py, coderabbit_quota.py). Keep orchestration in progression.py, delegate gate logic.

Files to Modify

• sova/supervisor/progression.py
• sova/supervisor/gates/__init__.py (new)
• sova/supervisor/gates/*.py (13 new gate modules)

Estimated Effort

4 hours

Dependencies

None

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Source: docs/HEALTH-AUDIT.md -- Health Audit 2026-08-12

Triage Assessment

Title: refactor(supervisor): split progression engine gate checks into modules
Has description: yes
Suitability: ready
Confidence: 85%
Complexity: moderate
Missing context: none
Labels: type: task, area: orchestrator

Issue has structured sections indicating clear scope; ready for research.