feat(migrate): add index migration CLI and core engine

- Add rvl migrate subcommand (helper, list, plan, apply, validate)
- Implement MigrationPlanner for schema diff classification
- Implement MigrationExecutor with drop_recreate mode
- Support vector quantization (float32 <-> float16) during migration
- Add MigrationValidator for post-migration validation
- Show error messages prominently on migration failure
- Add migration temp files to .gitignore

Author: nkanu17

.gitignore

@@ -234,3 +234,11 @@ tests/data
 
 # Local working directory (personal scripts, docs, tools)
 local/
+
+# Local notebooks (kept for development, not committed)
+docs/user_guide/13_index_migrations.ipynb
+
+# Migration temp files (generated by rvl migrate commands)
+migration_plan.yaml
+migration_report.yaml
+schema_patch.yaml

redisvl/cli/main.py

@@ -2,6 +2,7 @@
 import sys
 
 from redisvl.cli.index import Index
+from redisvl.cli.migrate import Migrate
 from redisvl.cli.stats import Stats
 from redisvl.cli.version import Version
 from redisvl.utils.log import get_logger
@@ -14,6 +15,7 @@ def _usage():
         "rvl <command> [<args>]\n",
         "Commands:",
         "\tindex       Index manipulation (create, delete, etc.)",
+        "\tmigrate     Index migration planning and execution",
         "\tversion     Obtain the version of RedisVL",
         "\tstats       Obtain statistics about an index",
     ]
@@ -49,3 +51,7 @@ def version(self):
     def stats(self):
         Stats()
         exit(0)
+
+    def migrate(self):
+        Migrate()
+        exit(0)