Add level-aware builder controls

docs/architecture.md

@@ -20,6 +20,12 @@ This project is intentionally being built in vertical slices.
 
 Authorization must be checked on the server for every mutation. Hiding an admin link is not authorization.
 
+Weapon and gear range calculations must preserve unrounded decimal endpoints
+and follow the empirically validated progression rules in
+[`STAT_LEVEL_SCALING.md`](STAT_LEVEL_SCALING.md). In particular, leveling is
+linear rather than compounded and game-matching integer values are truncated
+only at the presentation boundary.
+
 Local credentials are stored as Argon2id PHC strings with a unique random salt
 per password. Current work factors follow OWASP's 19 MiB / 2 iteration /
 single-lane minimum profile and can be increased over time; successful login
@@ -84,6 +90,36 @@ This guard prevents accidental merging or overwriting of contributor data.
 Stop the application before backup or restore so the embedded database file is
 not locked by another process.
 
+## Low-downtime development migrations
+
+The development database is a shared working data source: contributors may be
+entering ISAC records while application development continues. Database changes
+therefore use a prepared migration window rather than taking the server down at
+the beginning of implementation.
+
+Before the window, finish the code and idempotent migration, batch related
+schema changes, identify verification queries, and run `npm run check` plus
+`npm run build` while the server remains available. Prefer additive,
+backward-compatible tables and safely defaulted or nullable columns. Coordinate
+with known contributors so the stop does not interrupt an unsaved submission.
+
+The offline window is deliberately narrow:
+
+1. Inspect running processes and stop only this project's development server.
+2. Run and verify `npm run db:backup`.
+3. Run the already-prepared migration.
+4. Verify expected schema state, record counts, and critical entities.
+5. Restart the development server immediately.
+6. Confirm a basic page or health check, then perform extended browser and
+   regression testing with the service online.
+
+Code editing, builds, formatting, documentation review, and noncritical UI
+testing do not belong inside this window. Destructive, data-rewriting, or
+long-running migrations require a separately communicated maintenance window
+and a verified recovery plan. Every migration handoff reports the backup path,
+migration outcome, successful server restart, critical checks, and the
+approximate offline interval when available.
+
 # ISAC audit and compensating reversals
 
 Every successful ISAC mutation appends an event to `audit_log` through the