Replace native TreeView sidebar with a webview sidebar

[jeonghun-jj-lee]

Important

Problem: The Amicode sidebar is a native VS Code TreeDataProvider that clones the workspace file explorer — it cannot render custom UI (styled buttons, status pills, device lists) and has no awareness of which project the active session is bound to.

Approach: Replace the amicode.workspace view registration from type: "tree" to type: "webview". Implement a WebviewViewProvider with a vanilla TS/DOM browser entry point and a dedicated typed postMessage bridge. The sidebar renders a fixed header (Chat + New Project buttons), a session-aware unified project tree (Research Projects with lifecycle metadata + Dev Projects as plain nodes), and a fleet section placeholder.

Scope: The sidebar registration, provider, browser-side rendering, message bridge, project scanning, and session-to-project binding. Does NOT include fleet implementation (deferred), the in-app Rail concept (deferred), or a recently-deleted recovery section (future enhancement).

Assumptions: Research Projects are detected by project.toml presence (ADR 0012). Fleet section ships as a placeholder. The sidebar is navigation chrome — destinations open in the editor area. Sessions are bound to exactly one Project (ADR 0012).

Branching

• Base branch: amico/issue-663-research-projects
• Implementation branch: amico/issue-673-webview-sidebar
• PR target: amico/issue-663-research-projects (not main)

The sidebar's Research Project nodes depend on the project.toml detection and prescribed layout introduced by #663. The two features ship together.

Acceptance Criteria

Registration and build

• package.json registers amicode.workspace as type: "webview"
• SidebarViewProvider implements WebviewViewProvider with CSP-nonce HTML shell
• sidebar_webview.ts added as a browser entry point in esbuild.config.mjs (browser/iife)
• New sidebar_bridge.ts with typed message protocol (separate from chat_bridge.ts)
• Sidebar respects VS Code theme tokens (--vscode-sideBar-background, etc.)
• workspace_tree.ts and trees.ts are deleted

Fixed header

• Two half-width styled buttons rendered side by side: "Chat with Amico" and "+ New Project"
• Chat button opens/focuses ChatPanel in editor; dims when chat is already open
• New Project button triggers project creation flow (name, directory, project.toml scaffold)

Project tree

• Research Project nodes show name, lifecycle phase pill, last-active timestamp
• Research Project nodes expand to show file tree (lazy-loaded, respects files.exclude, hides .git)
• Research Project nodes show hover-revealed action icons (new session, open)
• Dev Projects and plain workspace folders show as expandable file tree nodes (no metadata)
• Right-click context menu on all node types with full file-operation parity: new file, new folder, rename, delete (trash only), copy path, copy relative path, reveal in Finder, open in terminal, open to side
• Research Project root nodes additionally offer "New Session" in context menu
• Workspace root nodes offer "Remove from Workspace"
• Delete always moves to trash (useTrash: true) — no permanent delete option

Session awareness

• Sidebar highlights and auto-expands the project bound to the active session
• Switching sessions (chat tabs) updates the sidebar's active project highlight
• No highlight when no session is open (Landing / fresh chat state)
• Clicking a non-active project only browses (expands file tree); does not switch sessions

Fleet (deferred)

• Fleet section present as a collapsible placeholder or hidden behind feature flag

Cleanup

• Existing workspace-tree tests removed or migrated

Key Decisions

Decision	Choice	Ref
Sidebar rendering	WebviewViewProvider (webview), not TreeDataProvider	ADR 0013
Rendering technology	Vanilla TS/DOM, no framework	ADR 0013
Communication	New sidebar_bridge.ts (typed postMessage)	—
Project + file model	Unified tree: Research Projects (rich) + Dev Projects (plain)	—
Session awareness	Sidebar follows active session; highlights bound project	—
Delete behavior	Trash only, no permanent delete	—
Fleet	Collapsible section, deferred	—
View registration	Replace amicode.workspace in-place, no coexistence	ADR 0013

Constraints & Invariants

• The sidebar is navigation chrome — it never hosts a chat surface or rich visualizations
• The sidebar follows sessions; it never drives session switching
• Directory tree is lazy-loaded (read on expand, not upfront)
• File operations reach parity with the deleted TreeView (context menus by node type)
• Delete always uses { useTrash: true } — no permanent deletion from the sidebar
• CSP nonce pattern matches existing webview panels (OnboardingPanel precedent)

Future Enhancements

• Recently Deleted section — in-sidebar recovery for trashed items (needs managed trash or OS-level restore integration)
• Fleet section — device list with name, role, connection status once fleet is formalized

Source

ADR 0013: docs/adr/0013-webview-sidebar.md