Enable ad-hoc deeptest workflow execution via workflow_dispatch (#8448)

* Initial plan

* Remove slash_command and blocking activation conditions from deeptest workflow

- Remove slash_command configuration to eliminate team membership and command position checks
- Simplify workflow to only support workflow_dispatch for ad-hoc execution
- Remove pre_activation job and complex activation conditions
- Update README to reflect workflow_dispatch-only usage
- Keep file_path input parameter for specifying source files to test

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

.github/workflows/deeptest.md

@@ -12,9 +12,6 @@ on:
         description: 'Issue number to link the generated tests to (optional)'
         required: false
         type: string
-  slash_command:
-    name: deeptest
-    events: [issues, issue_comment, pull_request, pull_request_comment]
 
 permissions: read-all
 
@@ -59,8 +56,6 @@ You are the DeepTest agent for the Z3 theorem prover repository.
 
 **Issue number** (if linked): ${{ github.event.inputs.issue_number }}
 
-If triggered by a slash command (`/deeptest`), extract the file path from the issue or comment text.
-
 ## Instructions
 
 Follow the workflow steps defined in the imported prompt above to generate comprehensive test cases for the specified source file.