docs(bf-11mft): document encryption test file verification

Add verification note confirming encryption test infrastructure already exists:
- test_encryption_errors.rs (12,690 bytes, 359 lines)
- Comprehensive module structure with 5 sub-modules
- All files compile successfully
- Infrastructure created in commit a0c3ebb2

Closes bf-11mft

notes/bf-11mft.md

@@ -0,0 +1,65 @@
+# bf-11mft: Encryption Test File Creation - Verification Note
+
+## Summary
+
+The encryption test file structure was already implemented in a previous commit (a0c3ebb2) as part of bead bf-5for4. The comprehensive test infrastructure exceeds the requirements of this bead.
+
+## Current State
+
+### Test Files Present
+
+The following encryption test files already exist:
+
+1. **`/home/coding/pdftract/crates/pdftract-cli/tests/test_encryption_errors.rs`** (12,690 bytes, 359 lines)
+   - Comprehensive module structure with multiple sub-modules:
+     - `unsupported_handlers` - Tests for Adobe LiveCycle unsupported handler
+     - `supported_encryption` - Tests for RC4/AES decryption with passwords
+     - `password_errors` - Tests for wrong/missing password handling
+     - `fixture_validation` - Validates encrypted PDF fixtures
+     - `integration_tests` - Placeholder for complete workflow tests
+   - Helper functions: `workspace_root()`, `encrypted_fixture_dir()`, `encrypted_fixture()`, `pdftract_bin()`
+   - Exit code constant: `ENCRYPTION_EXIT_CODE = 3`
+   - Fixture list constant: `ENCRYPTED_FIXTURES`
+
+2. **`/home/coding/pdftract/crates/pdftract-cli/tests/test_encryption_unsupported.rs`** (2,828 bytes)
+   - Focused tests for ENCRYPTION_UNSUPPORTED exit code
+   - Two specific tests for livecycle.pdf behavior
+
+3. **`/home/coding/pdftract/tests/encryption_errors.rs`** (7,018 bytes)
+   - Workspace-level encryption error tests
+   - Feature-gated with `#![cfg(feature = "decrypt")]`
+
+## Compilation Status
+
+✅ **All test files compile successfully**
+
+```bash
+cargo check --tests
+# No compilation errors
+```
+
+## Acceptance Criteria Status
+
+- ✅ **Test file created at the documented path**: `/home/coding/pdftract/crates/pdftract-cli/tests/test_encryption_errors.rs`
+- ✅ **File contains valid Rust module syntax**: Comprehensive module structure with proper imports and documentation
+- ✅ **File compiles without syntax errors**: Verified with `cargo check --tests`
+- ✅ **Basic test placeholder present**: Multiple test functions with `#[test]` and `#[ignore]` attributes
+
+## Notes
+
+The implemented test structure is significantly more comprehensive than the "basic module structure" requested in this bead. The file includes:
+
+- Full documentation with plan references (lines 258, 732, 1132, 1149)
+- Modular organization by encryption scenario
+- Fixture validation infrastructure
+- Exit code verification patterns
+- Password handling tests (marked `[ignore]` pending implementation)
+
+This comprehensive infrastructure was created in commit `a0c3ebb2` as part of bead `bf-5for4` (grep-corpus manifest schema), suggesting that encryption test infrastructure was implemented ahead of this bead.
+
+## References
+
+- Parent bead: bf-56jda
+- Previous bead: bf-2ntve (identified the test file location)
+- Plan line 258, Failure Mode Taxonomy: ENCRYPTION_UNSUPPORTED
+- Commit: a0c3ebb2 feat(bf-5for4): design manifest schema for grep-corpus