~/.graft/
  └── my-postgres/
      ├── config.json          ← State (schema v2)
      ├── graft.db             ← SQLite DAG (commits, tree_entries, refs)
      ├── objects/             ← BLAKE3 object pool (sharded by hash)
      │   ├── a1/
      │   │   └── b2c3d4e5f6…  ← Content-addressed blob
      │   └── f0/
      │       └── e1d2c3b4a5… ← Immutable, deduplicated
      └── branches/
          ├── main/            ← Materialized working branch
          └── experiment/      ← Another branch

Commit A (root: 0xabc)  ← initial main branch state
  └── Commit B (root: 0xdef, parent: 0xabc)  ← experiment checkout
        └── Commit C (root: 0x123, parent: 0xdef)  ← further change

1. Stop container
2. Run filesystem operation (commit, checkout, etc.)
3. Remove old container
4. Recreate container with bind mount → branch directory
5. Start container (if it was running before)

1. Look up parent branch's tip commit in SQLite
2. Get tree entries (file list + blob hashes) from the DAG
3. Materialize files from the object pool into the new branch directory
4. Set the new branch's ref to the parent's tip
5. Recreate the container with bind mount pointing at the new branch

1. Look up branch's tip commit
2. Get tree entries
3. Compute diff against current branch directory (walk + hash)
4. Only touch files that differ (added, removed, changed)
5. Prune empty directories
6. Recreate container with bind mount

1. Look up the target commit tree
2. Materialize those tree entries into the branch directory
3. Move the branch ref back to the target commit
4. Future commits extend from this point

1. Walk the branch directory
2. BLAKE3-hash every file
3. Build the Merkle tree
4. Compare computed root against stored root in the DAG
5. Report per-file differences (missing, extra, changed)

✓ Integrity OK (147 files, root f0e1d2)

✗ Integrity FAILED for experiment (2 changed, 1 missing)
  stored root: a1b2c3d
  actual root: f0e1d2

STATUS    FILE                    EXPECTED HASH   ACTUAL HASH
changed   base/16384/12547       a1b2c3d4e5f6…   f0e1d2c3b4a5…
missing   global/pg_control      9876543210ab…   (none)