Update additional usage pointers

* Remove obsolete/outdated content
* git-worktree:
  - Remove incorrect recommendation to copy the entire .serena folder
    in order to retain the cache (cache contains abs. paths)
  - Recommend to add the .serena folder to version control instead
    (which will not include the cache folder)

Relates to #805

docs/02-usage/999_additional-usage.md

@@ -3,30 +3,14 @@
 ## Prompting Strategies
 
 We found that it is often a good idea to spend some time conceptualizing and planning a task
-before actually implementing it, especially for non-trivial task. This helps both in achieving
-better results and in increasing the feeling of control and staying in the loop. You can
-make a detailed plan in one session, where Serena may read a lot of your code to build up the context,
-and then continue with the implementation in another (potentially after creating suitable memories).
-
-## Running Out of Context
-
-For long and complicated tasks, or tasks where Serena has read a lot of content, you
-may come close to the limits of context tokens. In that case, it is often a good idea to continue
-in a new conversation. Serena has a dedicated tool to create a summary of the current state
-of the progress and all relevant info for continuing it. You can request to create this summary and
-write it to a memory. Then, in a new conversation, you can just ask Serena to read the memory and
-continue with the task. In our experience, this worked really well. On the up-side, since in a
-single session there is no summarization involved, Serena does not usually get lost (unlike some
-other agents that summarize under the hood), and it is also instructed to occasionally check whether
-it's on the right track.
-
-Serena instructs the LLM to be economical in general, so the problem of running out of context
-should not occur too often, unless the task is very large or complicated.
+before actually implementing it, especially for non-trivial tasks. 
+For very complex tasks, you can make a detailed plan in one session, 
+where Serena may read a lot of your code to build up the context,
+and then continue with the implementation in another,
+having persisted the plan in a memory or dedicated file.
 
 ## Serena and Git Worktrees
 
 [git-worktree](https://git-scm.com/docs/git-worktree) can be an excellent way to parallelize your work. More on this in [Anthropic: Run parallel Claude Code sessions with Git worktrees](https://docs.claude.com/en/docs/claude-code/common-workflows#run-parallel-claude-code-sessions-with-git-worktrees).
 
-When it comes to serena AND git-worktree AND larger projects (that take longer to index), 
-the recommended way is to COPY your `$ORIG_PROJECT/.serena/cache` to `$GIT_WORKTREE/.serena/cache`. 
-Perform [pre-indexing of your project](indexing) to avoid having to re-index per each worktree you create. 
+Be sure to add the `.serena` folder to version control, such that your project-specific settings and memories are available across worktrees.