fix: remove --change from templates command

Templates are schema-level, not change-level. The command now uses
--schema instead of --change for consistency with how templates
are actually resolved.

Author: TabishB

openspec/changes/add-artifact-workflow-cli/design.md

@@ -28,7 +28,7 @@ Commands are top-level for maximum fluidity:
 openspec status --change <id>
 openspec next --change <id>
 openspec instructions <artifact> --change <id>
-openspec templates --change <id>
+openspec templates [--schema <name>]
 openspec new change <name>
 ```
 

openspec/changes/add-artifact-workflow-cli/proposal.md

@@ -13,7 +13,7 @@ This proposal adds CLI commands that expose the artifact workflow functionality
 - **NEW**: `openspec status --change <id>` shows artifact completion state
 - **NEW**: `openspec next --change <id>` shows artifacts ready to create
 - **NEW**: `openspec instructions <artifact> --change <id>` outputs enriched template
-- **NEW**: `openspec templates --change <id>` shows resolved template paths
+- **NEW**: `openspec templates [--schema <name>]` shows resolved template paths
 - **NEW**: `openspec new change <name>` creates a new change directory
 
 All commands are top-level for fluid UX. They integrate with existing core modules:

openspec/changes/add-artifact-workflow-cli/specs/cli-workflow/spec.md

@@ -74,14 +74,18 @@ The system SHALL output enriched instructions for creating an artifact.
 - **THEN** the system displays instructions with a warning about missing dependencies
 
 ### Requirement: Templates Command
-The system SHALL show resolved template paths for all artifacts.
+The system SHALL show resolved template paths for all artifacts in a schema.
 
-#### Scenario: List template paths
-- **WHEN** user runs `openspec templates --change <id>`
-- **THEN** the system displays each artifact with its resolved template path
+#### Scenario: List template paths with default schema
+- **WHEN** user runs `openspec templates`
+- **THEN** the system displays each artifact with its resolved template path using the default schema
+
+#### Scenario: List template paths with custom schema
+- **WHEN** user runs `openspec templates --schema tdd`
+- **THEN** the system displays template paths for the specified schema
 
 #### Scenario: Templates JSON output
-- **WHEN** user runs `openspec templates --change <id> --json`
+- **WHEN** user runs `openspec templates --json`
 - **THEN** the system outputs JSON mapping artifact IDs to template paths
 
 #### Scenario: Template resolution source