Pre-rc1 CCC docs updates
## Problem/motivation
Follow-up to:
#3586202
Address the docs/README issues from above issue.
## Solution
### Clarify Function-Call API Documentation
`docs/developers/function_calls.md` says the module provides one AI function call plugin, but the code ships multiple tools:
- `ai_context:get_relevant_ai_context_items`
- `ai_context:list_ai_context_items`
- `ai_context:load_ai_context_item_by_id`
This should be corrected before RC1 so tool IDs, behavior, and integration contracts are clear for downstream consumers.
### Document Scope Definition Alter Hook Centrally
`hook_ai_context_scope_info_alter()` exists through
`AiContextScopeManager::alterInfo('ai_context_scope_info')`, but it is not documented in `docs/developers/hooks.md`.
This should be documented before RC1 because scope plugins are a core extension point and altering definitions is part of that public API surface.
### Correct Stale README Architecture References
The README debugging section references removed or renamed architecture such as `AiContextRouter` and `AiContextScopeMatcher`. The upgrade notes correctly mention `AiContextScopeResolver`, but the debugging section should be brought into alignment.
The README requirements section also describes Dynamic Entity Reference as if it is a hard requirement, while `ai_context.info.yml` does not declare it and the module hides the target-entity scope when DER is absent.
These are not runtime blockers, but they should be fixed before RC1 because they affect install expectations and developer debugging.
## Tasks
- Update code
- Review
## AI usage disclosures
- [x] AI Assisted Issue
- [ ] AI Assisted Code
- [x] AI Generated Code
issue