feat(host-agent): make execution history authoritative

openspec/changes/task-execution-progress-visibility/specs/runtime-task-evidence/spec.md

@@ -1,38 +1,61 @@
 ## ADDED Requirements
 
 ### Requirement: Runtime persists complete evidence for each executed action
-The Runtime SHALL persist, for each action it attempts, a screenshot captured immediately before the executor call, the action description and arguments, the execution result, and a screenshot captured immediately after the executor call. Existing timeline records that contain only the legacy single screenshot SHALL remain readable, with that screenshot treated as the post-action image.
+The shared Runtime SHALL persist, for each action it attempts, a screenshot
+captured immediately before the executor call, the action description and
+arguments, the execution result, and a screenshot captured immediately after
+the executor call. Existing Timeline records that contain only the legacy
+single screenshot SHALL remain readable, with that screenshot treated as the
+post-action image.
 
 #### Scenario: An action succeeds
 - **WHEN** the Runtime executes an action for a task
-- **THEN** its timeline record includes distinct before and after screenshots, the action detail, and the execution result
+- **THEN** its Timeline record includes distinct before and after screenshots,
+  action detail, and execution result
 
 #### Scenario: An action fails
 - **WHEN** the Runtime executor exhausts its retries for an action
-- **THEN** the action's timeline record still includes any screenshots that were captured and the failure result before the task is marked failed
+- **THEN** the Timeline record still includes any captured screenshots and the
+  failure result before the task is marked failed
 
-#### Scenario: A legacy timeline record is read
-- **WHEN** a timeline record has only the prior `screenshot_path` field
-- **THEN** the Runtime exposes it as the post-action screenshot without failing to render the record
+#### Scenario: A legacy Timeline record is read
+- **WHEN** a Timeline record has only the prior `screenshot_path` field
+- **THEN** the Runtime exposes it as the post-action screenshot without
+  failing to render the record
 
-### Requirement: Runtime task evidence exposes available OCR observations
-The Runtime SHALL persist raw OCR observations associated with the scene used to plan an action when available, without adding duplicate OCR data to the LLM-facing normalized Scene payload. The Runtime task-detail UI SHALL render available OCR text, confidence, and bounds, and SHALL render normally when no OCR result exists.
+### Requirement: Runtime task evidence retains available OCR observations
+The shared Runtime SHALL persist raw OCR observations associated with the scene
+used to plan an action when available, without adding duplicate OCR data to the
+LLM-facing normalized Scene payload. The Host Agent task-detail UI SHALL render
+available OCR text, confidence, and bounds, and SHALL render normally when no
+OCR result exists.
 
 #### Scenario: OCR found text while planning an action
-- **WHEN** perception produced one or more OCR observations for the action's planning scene
-- **THEN** the corresponding timeline record includes those observations and the Runtime task-detail UI displays them
+- **WHEN** perception produced one or more OCR observations for the action's
+  planning scene
+- **THEN** the corresponding Timeline record includes those observations and
+  the Host Agent task-detail page displays them
 
 #### Scenario: OCR was unavailable or found no text
 - **WHEN** perception yields no OCR observations
-- **THEN** the Runtime records the action evidence and renders the task detail without an OCR result list
+- **THEN** the Runtime records the action evidence and the Host Agent task
+  detail renders without an OCR result list
 
-### Requirement: Runtime task evidence renders UI-tree inspection results
-When a Runtime step invokes the existing `get_ui_tree` or `ui_tree` tool and the persisted result contains normalized UI nodes, the Runtime task-detail UI SHALL render those nodes in a structured, collapsible view while retaining the recorded JSON result. The Runtime SHALL NOT change the tool's response contract or duplicate the result in a separate persistence field.
+### Requirement: Runtime task evidence retains UI-tree inspection results
+The Runtime SHALL retain a UI-tree inspection result when a step invokes the
+existing `get_ui_tree` or `ui_tree` tool and the result contains normalized
+nodes. The Host Agent task-detail UI SHALL render those nodes in a structured,
+collapsible view while retaining the recorded JSON result. The Runtime SHALL
+NOT change the tool response contract or duplicate the result in a separate
+persistence field.
 
 #### Scenario: UI-tree inspection succeeds
-- **WHEN** a task step uses `get_ui_tree` or `ui_tree` and returns one or more normalized nodes
-- **THEN** the task-detail UI displays each node's type, visible text or identifier, bounds, and available confidence
+- **WHEN** a task step uses `get_ui_tree` or `ui_tree` and returns one or
+  more normalized nodes
+- **THEN** the Host Agent task-detail page displays each node's type, visible
+  text or identifier, bounds, and available confidence
 
 #### Scenario: A non-UI-tree step is displayed
 - **WHEN** a task step did not invoke a UI-tree tool
-- **THEN** the task-detail UI does not render an empty UI-tree section
+- **THEN** the Host Agent task-detail page does not render an empty UI-tree
+  section