fix(tests): resolve pre-existing unit test failures in 5 feature files

Fix five pre-existing BDD test failures that were present on master
before PR #10988 was opened:

1. **architecture.feature** — Converted `IndexEntry` from `@dataclass` to
   Pydantic `BaseModel` and `ACMSIndex` to a plain class so the "all
   dataclasses should use Pydantic models" check passes.

2. **pr_compliance_checklist.feature** — Fixed `PROJECT_ROOT` path
   resolution from `parents[3]` to `parents[2]` so the agent definition
   file at `.opencode/agents/implementation-supervisor.md` is located
   correctly within the `/app` workspace.

3. **acms/index_data_model_and_traversal.feature** — Added missing Gherkin
   table header rows (`| key | value |` and `| filter | value |`) to the
   "Create an index entry" and "Combined query with multiple filters"
   scenarios so behave correctly resolves column references.

4. **cli_init_yes_flag.feature** — Added a `getattr` guard around
   `context.temp_dir` in `_restore_cwd()` so cleanup does not crash with
   a `TypeError` when `temp_dir` was never assigned.

5. **security_audit.feature** — Renamed the ACMS step from "the count
   should be {count:d}" to "the ACMS entry count should be {count:d}" to
   resolve a step ambiguity where ACMS's `step_check_entry_count_value`
   shadowed security_audit's `step_count_is`, causing `AttributeError` on
   `context.entry_count` for audit scenarios.

These failures are pre-existing on master and are independent of the
PassSuppressFormatter feature in the preceding commit. They are fixed in
a separate commit to maintain commit atomicity — the feature commit
remains solely about the output suppression change.

Refs: #10987

features/acms/index_data_model_and_traversal.feature

@@ -9,6 +9,7 @@ Feature: ACMS Index Data Model and File Traversal Engine
 
   Scenario: Create an index entry with file metadata
     When I create an index entry with:
+      | key | value |
       | path | /project/src/main.py |
       | file_type | python |
       | size_bytes | 1024 |
@@ -116,7 +117,7 @@ Feature: ACMS Index Data Model and File Traversal Engine
   Scenario: Get entry count from index
     Given I have an index with 10 entries
     When I get the entry count
-    Then the count should be 10
+    Then the ACMS entry count should be 10
 
   Scenario: Remove entry from index
     Given I have an index with 3 entries
@@ -131,6 +132,7 @@ Feature: ACMS Index Data Model and File Traversal Engine
       | /project/tests/test_main.py | python | test | cold |
       | /project/docs/readme.md | markdown | docs | cold |
     When I query the index with filters:
+      | filter | value |
       | path_pattern | src |
       | file_type | python |
       | tier | hot |