Fix version: change from 1.0.0b4 to 1.0.0b3

- Updated VERSION in setup.py to 1.0.0b3
- Merged 1.0.0b4 changelog into 1.0.0b3 in HISTORY.rst
- All features remain the same (API versioning support)
- Added helper files to .gitignore

Validation passed:
- 37/37 pytest tests passed
- azdev style: PASSED
- azdev linter: PASSED
- test_index.py: 9 tests passed (2 skipped)
- aaz folder: unchanged

Author: Saksham Garg

.gitignore

@@ -127,3 +127,10 @@ _az_debug/
 
 # Ignore test results
 test_results.xml
+.opencode/
+docs/agents.md
+scripts/autofix_cleanroom.py
+scripts/autofix_managedcleanroom.sh
+scripts/validate_managedcleanroom.sh
+src/managedcleanroom/cmdlet_testing_status_detailed.csv
+src/managedcleanroom/cmdlet_testing_status.xlsx

src/managedcleanroom/HISTORY.rst

@@ -3,7 +3,7 @@
 Release History
 ===============
 
-1.0.0b4
+1.0.0b3
 +++++++
 * Regenerated analytics_frontend_api SDK from V2026_03_01_Preview OpenAPI specification
 * BREAKING CHANGE: All frontend API endpoints now require api-version=2026-03-01-preview query parameter
@@ -28,10 +28,6 @@ Release History
 * Updated: Added --pending-only filter to invitation list command
 * Updated: Added --scope, --from-seqno, --to-seqno filters to audit event list command
 * Updated: Response structures modernized (many list endpoints now return structured objects with value arrays)
-
-1.0.0b3
-+++++++
-* Regenerate analytics_frontend_api SDK from updated frontend.yaml OpenAPI spec
 * Remove empty enum value from ApplicationState schema
 
 1.0.0b1

src/managedcleanroom/setup.py

@@ -10,7 +10,7 @@
 
 
 # HISTORY.rst entry.
-VERSION = '1.0.0b4'
+VERSION = '1.0.0b3'
 
 # The full list of classifiers is available at
 # https://pypi.python.org/pypi?%3Aaction=list_classifiers