Refresh docs: remove PROCESS.md, fix snapshot ID format, document pre-1.0 migration policy

docs/REPOSTRUCTURE.md

@@ -43,18 +43,19 @@ Blobs contain the actual file data from backups and must be encrypted for securi
 Each snapshot has its own subdirectory named with the snapshot ID.
 
 ### Snapshot ID Format
-- **Format**: `<hostname>-<YYYYMMDD>-<HHMMSSZ>`
-- **Example**: `laptop-20240115-143052Z`
+- **Format**: `<hostname>_<snapshot-name>_<RFC3339>` (or `<hostname>_<RFC3339>` if no
+  name was specified)
+- **Example**: `laptop_home_2024-01-15T14:30:52Z`
 - **Components**:
-  - Hostname (may contain hyphens)
-  - Date in YYYYMMDD format
-  - Time in HHMMSSZ format (Z indicates UTC)
+  - Short hostname (everything before the first dot is stripped from the FQDN)
+  - Snapshot name from the configured `snapshots:` map (optional)
+  - RFC3339 UTC timestamp
 
 ### Files in Each Snapshot Directory
 
-#### `db.zst.age` - Encrypted Database Dump
-- **What it contains**: Complete SQLite database dump for this snapshot
-- **Format**: SQL dump → Zstandard compressed → Age encrypted
+#### `db.zst.age` - Encrypted Database
+- **What it contains**: Pruned binary SQLite database for this snapshot
+- **Format**: Binary SQLite → Zstandard compressed → Age encrypted
 - **Encryption**: Encrypted with Age
 - **Purpose**: Contains full file metadata, chunk mappings, and all relationships
 - **Why encrypted**: Contains sensitive metadata like file paths, permissions, and ownership
@@ -67,7 +68,7 @@ Each snapshot has its own subdirectory named with the snapshot ID.
 - **Structure**:
 ```json
 {
-  "snapshot_id": "laptop-20240115-143052Z",
+  "snapshot_id": "laptop_home_2024-01-15T14:30:52Z",
   "timestamp": "2024-01-15T14:30:52Z",
   "blob_count": 42,
   "blobs": [