refactor(download): remove ProviderCore/download.py, move sanitize_filename to SYS.utils, replace callers to use API.HTTP.HTTPClient

docs/result_table.md

@@ -13,10 +13,11 @@ This document explains the `ResultTable` system used across the CLI and TUI: how
 
 - **ResultTable** (`SYS/result_table.py`)
   - Renders rows as a rich table and stores metadata used for selection expansion.
-  - Important APIs: `add_result()`, `set_table()`, `set_source_command()`, `set_row_selection_args()`, `set_table_metadata()`, and `select_interactive()`.
+  - Important APIs: `add_result()`, `set_table()`, `set_source_command()`, `set_row_selection_args()`, `set_row_selection_action()`, `set_table_metadata()`, and `select_interactive()`.
 
 - **ResultRow**
   - Holds columns plus `selection_args` (used for `@N` expansion) and `payload` (original object).
+  - Optionally stores `selection_action`, a full list of CLI tokens to run when `@N` selects this row. When present the CLI honors the explicit action instead of reconstructing it from `source_command` and `selection_args`.
 
 - **Provider selector**
   - If a provider implements `selector(selected_items, ctx=..., stage_is_last=True)`, it is run first when `@N` is used; if the selector returns `True` it has handled the selection (e.g., drilling into a folder and publishing a new ResultTable).
@@ -112,7 +113,7 @@ SearchResult(
 )
 ```
 
-Illustrative file SearchResult (after drilling):
+4. Otherwise, for single selections, CLI checks for `row.selection_action` and runs that verbatim if present; otherwise it expands `source_command + source_args + row_selection_args`. For multi-selections, items are piped downstream.
 
 ```py
 SearchResult(
@@ -217,6 +218,8 @@ Notes:
 
 ---
 
+For more detail on ResultTable provider authoring, see `docs/provider_authoring.md`.
+
 If you'd like, I can also:
 - Add provider-specific examples (AllDebrid, Bandcamp) into this doc ✅
 - Add a short checklist for PR reviewers when adding new providers