refactor(storage): delete dead session_links cycle-quarantine engine

[Sinity]

Summary

Completes the remaining polylogue-4ts.10 scope left as follow-up by #3643: deletes the dead async cycle-detection/quarantine engine in storage/sqlite/queries/session_links.py (zero production callers since #3643 ported the equivalent logic into the live writer), and retargets the three wrong-oracle tests that exercised only that dead engine at the real production write path (write_parsed_session_to_archive).

Problem

#3643 ported cycle detection + quarantine into the live session_links writer (write.py's _resolve_outbound_session_links / _resolve_session_graph), but left storage/sqlite/queries/session_links.py's equivalent async engine (upsert_session_links, resolve_session_links_for_session, resolve_unresolved_links_for_child, _would_create_cycle, _quarantine_link, count_quarantined_session_links) in place with zero production callers. Three tests exercised only that dead engine while implicitly or explicitly claiming to certify production behavior:

• tests/unit/insights/test_topology_cycle_rejection.py (a dedicated 621-line file bootstrapping a raw sqlite3 connection and calling the dead engine directly).
• test_delegation_direction_matches_real_link_resolver in test_delegations_view.py, whose docstring explicitly claimed to drive "the ACTUAL production write path" via the dead engine's functions.
• test_session_link_resolver_quarantines_cycle in the property write-path state machine, which manually inserted a session_links row and called the dead engine's resolve_unresolved_links_for_child to simulate a cycle.

This is exactly the wrong-oracle pattern flagged by the 2026-08-03 structural audit referenced on the bead: tests certifying behavior production code cannot exhibit.

Solution

• Deleted the dead write engine from queries/session_links.py, keeping only list_session_links_for_session (a genuine production read path reached via query_store_archive.py).
• Deleted tests/unit/insights/test_topology_cycle_rejection.py outright: its scenarios (two-node cycle, self-loop, diamond DAG) are already covered against the live path by test_topology_cycle_quarantine_live.py (landed with fix(storage): quarantine real cycles in the live session_links resolver #3643).
• Retargeted test_delegation_direction_matches_real_link_resolver to drive write_parsed_session_to_archive directly instead of the dead engine's upsert_session_links/resolve_session_links_for_session. Removed the now-unused _AsyncSqliteAdapter/_AsyncCursorAdapter shim built specifically to run the dead engine.
• Retargeted test_session_link_resolver_quarantines_cycle to reproduce the cycle via a real re-ingest through write_parsed_session_to_archive (matching the pattern in test_topology_cycle_quarantine_live.py) instead of manually inserting a row and calling the dead engine.
• Removed now-unused imports (aiosqlite, configure_connection, asyncio where no longer needed).

AC status (polylogue-4ts.10)

• AC1 (every write carries TopologyEdgeStatus/method, no empty-status writes): satisfied by fix(storage): quarantine real cycles in the live session_links resolver #3643, unaffected by this PR.
• AC2 (existing rows converge via ordinary derived-tier rebuild, no bespoke backfill): unaffected, no migration added.
• AC3 (a reader can filter edges by status, composition degrades visibly on a non-resolved parent): satisfied. list_session_links_for_session already returns status; downstream consumers already read it -- storage/insights/topology/derivation.py excludes quarantined edges from unresolved-edge composition, and insights/transforms.py threads child_link_status (including "quarantined") onto SubagentReport. Composition already degrades visibly: a quarantined edge's child never gets sessions.parent_session_id set, so it surfaces as its own root rather than silently composing through the rejected parent. No new reader surface was needed beyond confirming these existing paths.
• AC4 (live re-measure shows zero empty status/method rows): explicitly out of scope for this PR -- requires rebuilding the production index (polylogue ops reset --index && polylogued run), a separate operator action, not a code change.

Verification

• devtools test tests/unit/storage/test_delegations_view.py tests/unit/storage/test_topology_cycle_quarantine_live.py tests/unit/storage/test_unread_wire_batch_v46.py tests/unit/storage/test_archive_tiers_write.py tests/property/test_write_path_state_machine.py -- 120 passed
• devtools verify --quick -- exit 0 (ruff format/check, mypy --strict, render all --check, all lab policy gates)

Ref polylogue-4ts.10

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📥 Commits

Reviewing files that changed from the base of the PR and between b4558a9 and 6d5f8a1.

📒 Files selected for processing (4)

• polylogue/storage/sqlite/queries/session_links.py
• tests/property/test_write_path_state_machine.py
• tests/unit/insights/test_topology_cycle_rejection.py
• tests/unit/storage/test_delegations_view.py

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