fix(tui): add block cursor navigation bindings

ISSUES CLOSED: #10371

features/tdd_tui_block_cursor_navigation.feature

@@ -4,14 +4,8 @@ Feature: TDD Issue #10371 — Block cursor navigation (alt+up/alt+down) not impl
   This test captures bug #10371: the TUI application is missing ``alt+up``
   and ``alt+down`` key bindings for block cursor navigation.
 
-  The scenario is tagged ``@tdd_expected_fail`` so the underlying assertion
-  failure (confirming the bug exists) is inverted to a CI pass.  Once the
-  fix for #10371 is merged, remove the ``@tdd_expected_fail`` tag from the
-  scenario and this test will run normally as a regression guard.
-
   See CONTRIBUTING.md > Bug Fix Workflow > TDD Issue Test Tags.
 
-  @tdd_expected_fail
   Scenario: TUI app BINDINGS includes alt+up and alt+down for block cursor navigation
     Given the TUI app module is imported with mocked Textual
     When I inspect the TUI app BINDINGS for block cursor navigation

features/tui_app_coverage.feature

@@ -47,7 +47,7 @@ Feature: TUI App Coverage
     Given a mock command router and persona state
     When I instantiate the Textual TUI app
     Then the app class should have CSS_PATH set to "cleveragents.tcss"
-    And the app class should have 4 key bindings
+    And the app class should have 6 key bindings
 
   # --- compose method (lines 102-112) ---
 

src/cleveragents/tui/app.py

@@ -278,6 +278,8 @@ if _TEXTUAL_AVAILABLE:
             ("ctrl+q", "quit", "Quit"),
             ("f1", "help", "Help"),
             ("ctrl+t", "cycle_preset", "Cycle Preset"),
+            ("alt+up", "cursor_up", "Previous Block"),
+            ("alt+down", "cursor_down", "Next Block"),
             ("escape", "escape", "Close Overlay"),
         ]
 
@@ -313,6 +315,7 @@ if _TEXTUAL_AVAILABLE:
                 settings=load_conversation_settings()
             )
             self._conversation_stream.bootstrap(welcome_text="CleverAgents TUI")
+            self._block_cursor_index: int = 0
 
         def compose(self) -> Any:
             yield _Header(show_clock=True)
@@ -375,6 +378,15 @@ if _TEXTUAL_AVAILABLE:
             self._persona_state.cycle_preset(self._session.session_id)
             self._refresh_persona_bar()
 
+        def action_cursor_up(self) -> None:
+            """Move the block cursor to the previous transcript block."""
+            self._block_cursor_index = max(0, self._block_cursor_index - 1)
+
+        def action_cursor_down(self) -> None:
+            """Move the block cursor to the next transcript block."""
+            last_index = max(0, len(self._session.transcript) - 1)
+            self._block_cursor_index = min(last_index, self._block_cursor_index + 1)
+
         def action_escape(self) -> None:
             prompt = self.query_one("#prompt", PromptInput)