Refactored provider handling in Client to use OrderedMap, improvingconsistency and sorting. Added generic type annotations for OrderedMapand introduced a get_cached helper for cache management. This changesimplifies provider filtering and caching logic for models and info.

This change refactors the chat completion logic by moving it frominit.lua into a new completion.lua module. It also updates mappingsand setup to use the new module, improving code organization andmaintainability. Autocomplete setup is now handled in the completionmodule, and prompt listing is extracted to a helper function.Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

Previously, the resource preview header displayed the resource name, whichcould be missing. This change updates the header to show the resource URI,providing clearer context. Also, removes unused type annotations for improvedcode clarity.

Refactored chat window API to use `get_message(role, cursor)` and`get_block(role, cursor)` for both last and cursor-closest access.Removed legacy `get_closest_message` and `get_closest_block` methods.Updated mappings and documentation to reflect unified API. Thissimplifies usage and improves consistency for message/block retrievaland removal actions.

Adds support for displaying the assistant's reasoning above messages inthe chat UI as virtual text. Reasoning is now streamed and storedseparately from content, and models with reasoning capability areindicated in the model selector. This improves transparency of modelresponses and debugging.

Refactored Chat:get_block to properly select the closest block to thecursor, considering the role filter and ensuring correct fallback to thelast matching block. This improves accuracy when interacting with chatblocks in the UI.

Move role strings and plugin name to a dedicated constants module.Refactor all usages to reference the new constants. This improvesmaintainability and reduces duplication across the codebase.

Refactored chat and overlay constructors to remove redundant help argumentand use key_to_info for help and close mappings directly. This improvesclarity and maintainability by centralizing mapping logic and reducingparameter complexity.Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>