test: improve test coverage from 61% to 84.81%

Major improvements:
- Fixed all 42 broken tests (database connection leaks)
- Added db_connection() context manager for proper cleanup
- Created comprehensive test suites for undertested modules

New test coverage:
- tools/general_tools.py: 26 tests (97% coverage)
- tools/price_tools.py: 11 tests (validates NASDAQ symbols, date handling)
- api/price_data_manager.py: 12 tests (85% coverage)
- api/routes/results_v2.py: 3 tests (98% coverage)
- agent/reasoning_summarizer.py: 2 tests (87% coverage)
- api/routes/period_metrics.py: 2 edge case tests (100% coverage)
- agent/mock_provider: 1 test (100% coverage)

Database fixes:
- Added db_connection() context manager to prevent leaks
- Updated 16+ test files to use context managers
- Fixed drop_all_tables() to match new schema
- Added CHECK constraint for action_type
- Added ON DELETE CASCADE to trading_days foreign key

Test improvements:
- Updated SQL INSERT statements with all required fields
- Fixed date parameter handling in API integration tests
- Added edge case tests for validation functions
- Fixed import errors across test suite

Results:
- Total coverage: 84.81% (was 61%)
- Tests passing: 406 (was 364 with 42 failures)
- Total lines covered: 6364 of 7504

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

api/database.py

@@ -10,6 +10,7 @@ This module provides:
 import sqlite3
 from pathlib import Path
 import os
+from contextlib import contextmanager
 from tools.deployment_config import get_db_path
 
 
@@ -44,6 +45,37 @@ def get_db_connection(db_path: str = "data/jobs.db") -> sqlite3.Connection:
     return conn
 
 
+@contextmanager
+def db_connection(db_path: str = "data/jobs.db"):
+    """
+    Context manager for database connections with guaranteed cleanup.
+
+    Ensures connections are properly closed even when exceptions occur.
+    Recommended for all test code to prevent connection leaks.
+
+    Usage:
+        with db_connection(db_path) as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT * FROM jobs")
+            conn.commit()
+
+    Args:
+        db_path: Path to SQLite database file
+
+    Yields:
+        sqlite3.Connection: Configured database connection
+
+    Note:
+        Connection is automatically closed in finally block.
+        Uncommitted transactions are rolled back on exception.
+    """
+    conn = get_db_connection(db_path)
+    try:
+        yield conn
+    finally:
+        conn.close()
+
+
 def resolve_db_path(db_path: str) -> str:
     """
     Resolve database path based on deployment mode
@@ -431,10 +463,9 @@ def drop_all_tables(db_path: str = "data/jobs.db") -> None:
 
     tables = [
         'tool_usage',
-        'reasoning_logs',
-        'trading_sessions',
+        'actions',
         'holdings',
-        'positions',
+        'trading_days',
         'simulation_runs',
         'job_details',
         'jobs',
@@ -494,7 +525,7 @@ def get_database_stats(db_path: str = "data/jobs.db") -> dict:
         stats["database_size_mb"] = 0
 
     # Get row counts for each table
-    tables = ['jobs', 'job_details', 'positions', 'holdings', 'trading_sessions', 'reasoning_logs',
+    tables = ['jobs', 'job_details', 'trading_days', 'holdings', 'actions',
               'tool_usage', 'price_data', 'price_data_coverage', 'simulation_runs']
 
     for table in tables:

api/migrations/001_trading_days_schema.py

@@ -66,7 +66,7 @@ def create_trading_days_schema(db: "Database") -> None:
             completed_at TIMESTAMP,
 
             UNIQUE(job_id, model, date),
-            FOREIGN KEY (job_id) REFERENCES jobs(job_id)
+            FOREIGN KEY (job_id) REFERENCES jobs(job_id) ON DELETE CASCADE
         )
     """)
 
@@ -101,7 +101,7 @@ def create_trading_days_schema(db: "Database") -> None:
             id INTEGER PRIMARY KEY AUTOINCREMENT,
             trading_day_id INTEGER NOT NULL,
 
-            action_type TEXT NOT NULL,
+            action_type TEXT NOT NULL CHECK(action_type IN ('buy', 'sell', 'hold')),
             symbol TEXT,
             quantity INTEGER,
             price REAL,