feat(vscode-ail-chat): toggle side panel — run history + pipeline steps trees [Unit 4]

[AlexChesser]

Part of #162. Depends on #163 (vscode stub). Can be worked in parallel with #164/#165.

Problem

There is no way to inspect past runs or browse the active pipeline's steps without opening the YAML file manually. The user has no audit trail and no step-navigation shortcut.

Solution

Two new tree views in the ail-chat-sidebar container, hidden by default behind a toggle button in the chat view's title bar.

Toggle mechanism

let panelVisible = false;
commands.registerCommand('ail-chat.toggleInfoPanel', () => {
  panelVisible = !panelVisible;
  void commands.executeCommand('setContext', 'ail-chat.panelVisible', panelVisible);
});

Views use "when": "ail-chat.panelVisible" in package.json so they appear/disappear without disposal.

Run History tree (ail-chat.historyView)

• RunHistoryProvider stores { runId, prompt, timestamp, logPath } in workspaceState
• logPath is computed at record time: ~/.ail/projects/<sha1(cwd)>/runs/<runId>.jsonl — not at click time, so workspace changes don't lose history
• Capped at 100 entries (evict oldest on overflow)
• addRun(runId, prompt, cwd) called by ChatViewProvider on each run_started event
• Tree item: first 60 chars of prompt + relative timestamp

ail-chat.openRunLog command:

1. Read logPath from the RunItem
2. Parse NDJSON, format as readable text (step IDs, responses, costs, errors)
3. vscode.workspace.openTextDocument({ content, language: 'log' }) + showTextDocument — no webview message; native document gives find/copy/folding for free

Pipeline Steps tree (ail-chat.stepsView)

• PipelineStepsProvider reads the active pipeline YAML via the yaml package (already a dep)
• Top-level steps only — sub-pipeline references (pipeline: ./workflows/foo.ail.yaml) render as a single node labelled with the filename; no recursion
• Error node (no expand) when pipeline is missing, YAML is malformed, or in passthrough mode
• Each item: step id + type icon (prompt/context/skill/sub-pipeline)

ail-chat.openStep command:

1. vscode.window.showTextDocument(vscode.Uri.file(pipelinePath))
2. Search for the step id: line → editor.revealRange(..., InCenter)

Files

New:

• vscode-ail-chat/src/history-tree-provider.ts
• vscode-ail-chat/src/steps-tree-provider.ts
• vscode-ail-chat/test/history-tree-provider.test.ts
• vscode-ail-chat/test/steps-tree-provider.test.ts

Modified:

• vscode-ail-chat/src/extension.ts — register both providers + toggle command
• vscode-ail-chat/src/chat-view-provider.ts — call historyProvider.addRun(...) on run_started; call stepsProvider.refresh(pipeline) on pipeline change
• vscode-ail-chat/package.json:
  • New views with when: ail-chat.panelVisible
  • ail-chat.toggleInfoPanel command + $(layout-sidebar-right) icon
  • menus.view/title entry for the toggle button
  • ail-chat.openRunLog and ail-chat.openStep commands

Reference implementations: vscode-ail/src/views/HistoryTreeProvider.ts (152 lines) and vscode-ail/src/views/StepsTreeProvider.ts (185 lines) — match tree-item shape and contextValue conventions, but adapt to the chat extension's state model.

Test coverage (requires vscode stub from #163)

history-tree-provider.test.ts:

• addRun stores entry with correct logPath computed from cwd
• 101st entry evicts the oldest
• workspaceState round-trip (mock the context)
• getChildren returns entries reverse-chronological

steps-tree-provider.test.ts:

• Valid multi-step pipeline → one StepItem per top-level step
• Sub-pipeline reference → single node with filename label
• Malformed YAML → error node, no throw
• Null pipeline (passthrough) → empty tree

Verification

1. Toggle button in chat view title → "Run History" and "Pipeline Steps" appear; click again → disappear
2. Run two prompts → both appear in history; click one → VS Code opens the run log as a log-language document
3. Open a multi-step pipeline → steps tree shows top-level steps; click a step → YAML opens at that id: line, revealed in viewport
4. npm test passes

Risk

Low. Tree views are hidden by default; toggle is fully opt-in.