fix(sqlite): disable graph mmap across peer checkpoints

[ScriptedAlchemy]

Summary

• disable mmap on graph DB read/write and read-only connections
• preserve ordinary file I/O across overlapping daemon/watcher peers
• add mixed 8192→4096 consolidation and watcher checkpoint regression

Tests

• cargo test --lib mixed_page_destination_survives_overlapping_watcher_opens -- --nocapture
• db connection tests (11 passed)
• cargo fmt --all -- --check
• cargo clippy --lib -- -D warnings

Live dogfood: closes the highest-confidence corruption window observed after the v0.0.52 recovery.

[changeset-bot]

⚠️ No Changeset found

Latest commit: d951204

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