fix: ensure DB connections are fully released on close

[monodera]

Summary

• TargetDB.close() was calling session.close() only, which returns connections to SQLAlchemy's internal pool but does not close the underlying TCP sockets to PostgreSQL.
• On abnormal process termination (unhandled exceptions, SIGINT, etc.) the engine is never garbage-collected, causing idle connections to accumulate on the PostgreSQL server.
• Added engine.dispose() to close() to fully release all pooled connections to the server.
• Added __enter__ / __exit__ to support the with statement for safer usage.

Root cause

# Before: session is returned to pool, TCP socket stays open
def close(self):
    self.session.close()

# After: pool is disposed, TCP sockets are closed server-side
def close(self):
    self.session.close()
    self.engine.dispose()

Test plan

• Verify that after calling db.close(), the connection no longer appears in pg_stat_activity
• Verify that existing workflows using TargetDB continue to work normally
• Verify context manager usage: with TargetDB(...) as db: ...

🤖 Generated with Claude Code

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 5 complexity · 0 duplication

Metric	Results
Complexity	5
Duplication	0

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[Copilot]

Pull request overview

This PR improves lifecycle management for TargetDB by fully releasing SQLAlchemy pooled connections when closing, and adds context manager support to encourage safer usage patterns.

Changes:

• Update TargetDB.close() to call engine.dispose() after session.close() so pooled DB connections are fully released.
• Add TargetDB.__enter__ / __exit__ to enable with TargetDB(...) as db: usage.
• Regenerate/update tbls-generated table documentation (index ordering changes only).

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
src/targetdb/targetdb.py	Disposes SQLAlchemy engine on close and adds context manager support.
docs/tbls/public.target.md	Updates generated index listing order/formatting.
docs/tbls/public.sky.md	Updates generated index listing order/formatting.
docs/tbls/public.fluxstd.md	Updates generated index listing order/formatting.

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