fix: disable graph DB mmap before WAL

[ScriptedAlchemy]

Summary

• move graph DB PRAGMA mmap_size ahead of journal_mode = WAL
• mirror the GlobalDb Windows mmap ordering used by fix: disable GlobalDb mmap on Windows #115
• target the Windows 6/8 master failure from run 28077056988, where mcp_handler_test aborted with 0xc0000005/os error 998

Verification

• cargo fmt --check
• cargo test -p tracedecay --test mcp_handler_test path_containment_read_rejects_parent_traversal_before_serving_file -- --exact
• cargo test -p tracedecay --test mcp_handler_test test_by_qualified_name_finds_indexed_node -- --exact
• cargo test -p tracedecay mmap -- --nocapture

[changeset-bot]

⚠️ No Changeset found

Latest commit: aa508af

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR