fix(cli): add agents validation list command to validation CLI

Implements the missing 'agents validation list' command as required by the
CleverAgents CLI specification (v3.2.0+). The command lists all registered
validations from the tool registry with support for:

- Filtering by namespace (--namespace/-n)
- Filtering by source type (--source/-s)
- Filtering by regex pattern on validation names (--pattern/-p)
- Multiple output formats (--format/-f): rich, json, yaml, plain, table

The implementation follows the same pattern as 'agents tool list' and other
list commands in the CLI, ensuring consistency across the command surface.

Changes from TDD commit:
- Removes @tdd_expected_fail tags (tests now pass with implementation)
- Changes regex positional Argument to --pattern/-p Option for API consistency
  with agents tool list which uses --pattern as a named Option
- Extracts _get_name nested function to module-level _get_validation_name
  following the module's established helper convention

ISSUES CLOSED: #8621

features/validation_list_command.feature

@@ -9,36 +9,36 @@ Feature: Validation list command
 
   # --- Basic list functionality ---
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List all validations
     Given there are mocked validations in the registry
     When I run validation CLI list
     Then the validation CLI list should show all validations
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with namespace filter
     Given there are mocked validations in the registry
     When I run validation CLI list with namespace filter "local"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with source filter
     Given there are mocked validations in the registry
     When I run validation CLI list with source filter "custom"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with regex filter
     Given there are mocked validations in the registry
     When I run validation CLI list with regex filter "coverage-.*"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with invalid regex
     When I run validation CLI list with invalid regex "[invalid"
     Then the validation CLI command should abort
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations when empty
     Given there are no mocked validations
     When I run validation CLI list
@@ -46,31 +46,31 @@ Feature: Validation list command
 
   # --- Format support ---
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with json format
     Given there are mocked validations in the registry
     When I run validation CLI list with format "json"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with yaml format
     Given there are mocked validations in the registry
     When I run validation CLI list with format "yaml"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with table format
     Given there are mocked validations in the registry
     When I run validation CLI list with format "table"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with plain format
     Given there are mocked validations in the registry
     When I run validation CLI list with format "plain"
     Then the validation CLI list should succeed with results
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: List validations with rich format (default)
     Given there are mocked validations in the registry
     When I run validation CLI list with format "rich"
@@ -78,7 +78,7 @@ Feature: Validation list command
 
   # --- Help text ---
 
-  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  @tdd_issue @tdd_issue_8621
   Scenario: Validation help shows list subcommand
     When I run validation CLI help
     Then the validation CLI help should show "list" as a subcommand

src/cleveragents/cli/commands/validation.py

@@ -109,6 +109,13 @@ def _validation_spec_dict(tool: Any) -> dict[str, Any]:
     return {"name": str(tool)}
 
 
+def _get_validation_name(v: Any) -> str:
+    """Return the name string for a validation object or dict."""
+    if isinstance(v, dict):
+        return str(v.get("name", ""))
+    return str(getattr(v, "name", ""))
+
+
 def _attachment_dict(attachment: Any) -> dict[str, Any]:
     """Convert an attachment to a plain dict for output formatting."""
     if isinstance(attachment, dict):
@@ -272,9 +279,13 @@ def list_validations(
         str | None,
         typer.Option("--source", "-s", help="Filter by source type"),
     ] = None,
-    regex: Annotated[
+    pattern: Annotated[
         str | None,
-        typer.Argument(help="Optional regex pattern to filter validation names"),
+        typer.Option(
+            "--pattern",
+            "-p",
+            help="Filter validation names by regex pattern",
+        ),
     ] = None,
     fmt: Annotated[
         str,
@@ -287,7 +298,7 @@ def list_validations(
         agents validation list
         agents validation list --namespace local
         agents validation list --source custom
-        agents validation list "coverage-.*"
+        agents validation list --pattern "coverage-.*"
         agents validation list --format json
     """
     try:
@@ -299,19 +310,18 @@ def list_validations(
         )
 
         # Apply regex filter if provided
-        if regex:
+        if pattern:
             try:
-                pattern = re.compile(regex)
+                compiled_pattern = re.compile(pattern)
             except re.error as exc:
-                console.print(f"[red]Invalid regex pattern:[/red] {regex}")
+                console.print(f"[red]Invalid regex pattern:[/red] {pattern}")
                 raise typer.Abort() from exc
 
-            def _get_name(v: Any) -> str:
-                if isinstance(v, dict):
-                    return str(v.get("name", ""))
-                return str(getattr(v, "name", ""))
-
-            validations = [v for v in validations if pattern.search(_get_name(v))]
+            validations = [
+                v
+                for v in validations
+                if compiled_pattern.search(_get_validation_name(v))
+            ]
 
         if not validations:
             console.print("[yellow]No validations found.[/yellow]")