fix: prevent extension command shadowing (#1994)

* fix: prevent extension command shadowing

* Validate extension command namespaces

* Reuse extension command name pattern

extensions/EXTENSION-API-REFERENCE.md

@@ -44,7 +44,7 @@ provides:
     - name: string       # Required, pattern: ^speckit\.[a-z0-9-]+\.[a-z0-9-]+$
       file: string       # Required, relative path to command file
       description: string # Required
-      aliases: [string]  # Optional, array of alternate names
+      aliases: [string]  # Optional, same pattern as name; namespace must match extension.id and must not shadow core or installed extension commands
 
   config:                # Optional, array of config files
     - name: string       # Config file name

extensions/EXTENSION-DEVELOPMENT-GUIDE.md

@@ -41,7 +41,7 @@ provides:
     - name: "speckit.my-ext.hello"      # Must follow pattern: speckit.{ext-id}.{cmd}
       file: "commands/hello.md"
       description: "Say hello"
-      aliases: ["speckit.hello"]        # Optional aliases
+      aliases: ["speckit.my-ext.hi"]    # Optional aliases, same pattern
 
   config:                               # Optional: Config files
     - name: "my-ext-config.yml"
@@ -186,7 +186,7 @@ What the extension provides.
 - `name`: Command name (must match `speckit.{ext-id}.{command}`)
 - `file`: Path to command file (relative to extension root)
 - `description`: Command description (optional)
-- `aliases`: Alternative command names (optional, array)
+- `aliases`: Alternative command names (optional, array; each must match `speckit.{ext-id}.{command}`)
 
 ### Optional Fields
 

extensions/EXTENSION-USER-GUIDE.md

@@ -214,8 +214,8 @@ Extensions add commands that appear in your AI agent (Claude Code):
 # In Claude Code
 > /speckit.jira.specstoissues
 
-# Or use short alias (if provided)
-> /speckit.specstoissues
+# Or use a namespaced alias (if provided)
+> /speckit.jira.sync
 ```
 
 ### Extension Configuration

extensions/RFC-EXTENSION-SYSTEM.md

@@ -223,7 +223,7 @@ provides:
     - name: "speckit.jira.specstoissues"
       file: "commands/specstoissues.md"
       description: "Create Jira hierarchy from spec and tasks"
-      aliases: ["speckit.specstoissues"]  # Alternate names
+      aliases: ["speckit.jira.sync"]  # Alternate names
 
     - name: "speckit.jira.discover-fields"
       file: "commands/discover-fields.md"
@@ -1517,7 +1517,7 @@ specify extension add github-projects
 /speckit.github.taskstoissues
 ```
 
-**Compatibility shim** (if needed):
+**Migration alias** (if needed):
 
 ```yaml
 # extension.yml
@@ -1525,10 +1525,10 @@ provides:
   commands:
     - name: "speckit.github.taskstoissues"
       file: "commands/taskstoissues.md"
-      aliases: ["speckit.taskstoissues"]  # Backward compatibility
+      aliases: ["speckit.github.sync-taskstoissues"]  # Alternate namespaced entry point
 ```
 
-AI agent registers both names, so old scripts work.
+AI agents register both names, so callers can migrate to the alternate alias without relying on deprecated global shortcuts like `/speckit.taskstoissues`.
 
 ---
 

extensions/template/extension.yml

@@ -47,8 +47,8 @@ provides:
     - name: "speckit.my-extension.example"
       file: "commands/example.md"
       description: "Example command that demonstrates functionality"
-      # Optional: Add aliases for shorter command names
-      aliases: ["speckit.example"]
+      # Optional: Add aliases in the same namespaced format
+      aliases: ["speckit.my-extension.example-short"]
 
     # ADD MORE COMMANDS: Copy this block for each command
     # - name: "speckit.my-extension.another-command"