test(coverage): add Behave BDD tests to improve unit test coverage across 53 source modules

Add 53 new .feature files and corresponding step definition files targeting
uncovered lines identified in build/coverage.xml. Fix AmbiguousStep conflicts
in 7 pre-existing step files by disambiguating step text.

New tests cover: ACP clients/facade, actor CLI/config, application container,
ACMS service/strategies, async worker, automation profile CLI, autonomy
guardrail, bridge, change model, config CLI/service, context service,
cross-plan correction, database models, decision service, decomposition
clustering/service, discovery handler, langchain chat provider, langgraph
nodes, materializers, multi-project service, plan apply/CLI/lifecycle/model/
preflight/resume/service, PostgreSQL analyzer, project CLI/context CLI,
provider registry, reactive application/route, repositories, resolver handler,
resource registry service, resume model, retry patterns, sandbox protocol,
server CLI, skill CLI/service, skills registry, subplan execution/service,
system CLI, UKO loader, UoW, and YAML template engine.

Closes #645

features/skill_service_coverage_boost.feature

@@ -0,0 +1,111 @@
+@phase1 @domain @skill_service_coverage
+Feature: SkillService uncovered code paths
+  As a developer maintaining the SkillService
+  I want comprehensive test coverage for defensive guards, exception
+  handling in database persistence, and the update-persist path
+  So that edge cases and failure modes are verified
+
+  # ────────────────────────────────────────────────────────
+  # add_skill: None config guard (line 95)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_none_config
+  Scenario: add_skill raises ValueError when config is None
+    Given a skill service without persistence
+    When I call add_skill with a None config
+    Then a ssc ValueError should be raised with message "config cannot be None"
+
+  # ────────────────────────────────────────────────────────
+  # _load_from_db: early return when repo is None (line 278)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_load_no_repo
+  Scenario: _load_from_db returns immediately when no repo is set
+    Given a skill service without persistence
+    When I explicitly call _load_from_db
+    Then the skills cache should remain empty
+    And no ssc error should be raised
+
+  # ────────────────────────────────────────────────────────
+  # _load_from_db: exception handling (lines 287-288)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_load_db_error
+  Scenario: _load_from_db logs warning when list_all raises an exception
+    Given a mock skill repo that raises on list_all
+    When I create a skill service with the failing repo
+    Then the skills cache should remain empty
+    And a warning about failed database load should be logged
+
+  # ────────────────────────────────────────────────────────
+  # _persist_skill: update path (line 298)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_persist_update
+  Scenario: Updating an existing skill calls repo.update instead of repo.create
+    Given a skill service with a mock repo and session factory
+    And I add a skill "local/update-target" via config
+    When I update the skill "local/update-target" via add_skill with update flag
+    Then the mock repo update method should have been called
+    And the mock repo create method should have been called once
+
+  # ────────────────────────────────────────────────────────
+  # _persist_skill: exception handling on create (lines 300-304)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_persist_create_error
+  Scenario: _persist_skill logs warning when repo.create raises
+    Given a mock skill repo that raises on create
+    And a skill service with the failing-create repo
+    When I add a skill "local/fail-persist" via config ignoring persist errors
+    Then the skill should still be in the in-memory cache
+    And a warning about failed persist should be logged
+
+  # ────────────────────────────────────────────────────────
+  # _persist_skill: exception handling on update (lines 300-304)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_persist_update_error
+  Scenario: _persist_skill logs warning when repo.update raises
+    Given a mock skill repo that raises on update
+    And a skill service with the failing-update repo
+    And I add a new skill "local/upd-fail" to the service
+    When I update skill "local/upd-fail" with update flag ignoring persist errors
+    Then the updated skill should be in the in-memory cache
+    And a warning about failed persist on update should be logged
+
+  # ────────────────────────────────────────────────────────
+  # _delete_skill_from_db: exception handling (lines 314-318)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_delete_db_error
+  Scenario: _delete_skill_from_db logs warning when repo.delete raises
+    Given a mock skill repo that raises on delete
+    And a skill service with the failing-delete repo
+    And I add a skill "local/del-fail" to the failing-delete service
+    When I remove skill "local/del-fail" from the service
+    Then the skill should be removed from the in-memory cache
+    And a warning about failed database delete should be logged
+
+  # ────────────────────────────────────────────────────────
+  # _commit: early return when no session_factory (line 324)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_commit_no_session
+  Scenario: _commit returns early when session_factory is None
+    Given a skill service with a mock repo but no session factory
+    When I add a skill "local/no-session" via config on the no-session service
+    Then the skill should be in the no-session service cache
+    And no ssc error should be raised
+
+  # ────────────────────────────────────────────────────────
+  # _commit: exception handling (lines 328-329)
+  # ────────────────────────────────────────────────────────
+
+  @ssc_commit_error
+  Scenario: _commit logs warning when session.commit raises
+    Given a mock session factory that raises on commit
+    And a skill service with a mock repo and the failing session factory
+    When I add a skill "local/commit-fail" via config on the failing-commit service
+    Then the skill should be in the failing-commit service cache
+    And a warning about failed session commit should be logged