Add activation_command to project config (#1623)

Add activation_command to project config

Adds two optional fields to ProjectConfig:
- activation_command: shell command run in the project root before the
  language backend (LSP or JetBrains) initialises
- activation_command_timeout: safety backstop (default 180s); on expiry
  the process tree is killed and activation continues

The command is only executed for trusted projects (trusted_project_path_patterns).
Exit code is the primary completion signal; failures and timeouts are logged
but never abort activation (no return channel to the LLM at that point).

Closes #1606

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Co-authored-by: Dominik Jain <dominik.jain@oraios-ai.de>

docs/02-usage/040_workflow.md

@@ -53,6 +53,7 @@ The file allows you to configure ...
   * write access
   * [additional workspace folders](additional-workspace-folders) for cross-package reference support in monorepos
   * an initial prompt that shall be passed to the LLM whenever the project is activated
+  * a shell command to run upon project activation (prior to language backend initialisation)
   * the set of tools and modes to use for the project
   * and some other settings.