docs(v3): add Mission Control redesign planning docs

v3 architecture planning: task plan with core concept, user requirements,
and architecture questions for adversarial review. Findings doc with
codebase reuse analysis (keep/replace/drop). Progress log for v3 sessions.

docs/v3-findings.md

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+# BTerminal v3 — Research Findings
+
+## Current Codebase Reuse Analysis
+
+### Can Reuse (with modifications)
+- **Agent session infrastructure**: AgentPane, agent store, agent dispatcher, SDK messages adapter, sidecar bridge — core agent functionality stays
+- **Terminal infrastructure**: TerminalPane, pty-bridge — terminal rendering unchanged
+- **Markdown rendering**: MarkdownPane, highlight utils — markdown viewer stays
+- **Sidecar management**: SidecarManager, agent-runner.mjs — backend agent orchestration
+- **PTY management**: PtyManager — backend terminal management
+- **Session persistence**: session-bridge, SessionDb — needs schema extension for projects
+- **Theme system**: theme store, catppuccin CSS — visual layer unchanged
+- **Notification system**: toast notifications — stays as-is
+- **Claude bridge**: profiles + skills — reusable per project
+- **StatusBar**: needs redesign but concept stays
+
+### Must Replace
+- **Layout store**: Current pane-based grid system → project-based workspace system
+- **TilingGrid**: CSS Grid tiling → project box layout with internal structure
+- **SessionList sidebar**: Pane list → project/group navigation
+- **App.svelte**: Root layout completely changes
+- **Settings dialog**: Per-app settings → per-project settings
+
+### Can Drop
+- **Detached pane mode**: Doesn't fit the workspace model
+- **Drag-resize splitters**: Project boxes have fixed internal layout
+- **Layout presets (1-col, 2-col, etc.)**: Replaced by N-project horizontal layout
+- **Remote machine integration**: Defer to v4 (complexity too high to combine)
+- **ctx ContextPane**: Becomes a workspace tab instead of a pane type
+
+---
+
+## Adversarial Agent Findings
+
+(To be filled by adversarial review agents)

docs/v3-progress.md

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+# BTerminal v3 — Progress Log
+
+### Session: 2026-03-07 — Architecture Planning
+
+#### Phase: Adversarial Design Review
+- [ ] Launch architecture agents (advocate, devil's advocate, synthesizer)
+- [ ] Collect findings
+- [ ] Produce final architecture plan
+- [ ] Create implementation phases

docs/v3-task_plan.md

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+# BTerminal v3 — Mission Control Redesign
+
+## Goal
+
+Transform BTerminal from a multi-pane terminal/agent tool into a **multi-project mission control** — a helm for managing multiple development projects simultaneously, each with its own Claude agent session, team agents, terminals, and settings.
+
+## Status: Planning — Rev 0
+
+---
+
+## Core Concept
+
+**Project Groups** are workspaces. Each group has up to 5 projects arranged horizontally. One group visible at a time. Projects have their own Claude subscription, working directory, icon, and settings. The app is a dashboard for orchestrating Claude agents across a portfolio of projects.
+
+### Key Mental Model
+
+```
+BTerminal v2: Terminal emulator with agent sessions (panes in a grid)
+BTerminal v3: Project orchestration dashboard (projects in a workspace)
+```
+
+### User Requirements (verbatim)
+
+1. Projects arranged in **project groups** (many groups, switch between them)
+2. Each group has **up to 5 projects** shown horizontally
+3. Group/project config via **main menu** (command palette / hidden drawer, on keystroke)
+4. Per-project settings:
+   - Claude subscription (multi-account via switcher-claude)
+   - Working directory
+   - Project icon (nerd font, suggested but settable)
+   - Project name
+   - Project identifier (derived from name, lowercase-dashed, settable)
+   - Project description (optional)
+   - Enabled flag (bool)
+5. Project group = workspace on screen
+6. Each project box has:
+   - **Claude session box** (default open, continues previous session)
+   - **Team agents window** (to the right, shows spawned subagents)
+   - **Terminal tabs below** (agent terminals + user terminals, tabbed)
+7. **3 workspace tabs**:
+   - Tab 1: Sessions view (described above)
+   - Tab 2: MD file viewer (auto-discovered from projects, choosable)
+   - Tab 3: Settings editor (per-project settings)
+8. App launchable with `--group <name>` CLI arg
+9. JSON config file defines all groups
+10. Session continuity: resume previous + restore history visually
+11. SSH sessions: spawnable within a project's terminal tabs or in separate tabs
+12. ctx viewer: separate tab
+
+---
+
+## Architecture Questions for Adversarial Review
+
+1. **Config format**: JSON file vs SQLite for group/project definitions?
+2. **Layout engine**: How to arrange up to 5 project boxes with internal subdivisions?
+3. **Session isolation**: One sidecar per project? Shared sidecar with project context?
+4. **State management**: How to handle workspace switching (mount/unmount vs hide/show)?
+5. **What survives from v2**: Which components/stores/adapters carry over?
+6. **Tab implementation**: Browser-style tabs or Svelte component switching?
+7. **Command palette**: Build custom or use a library?
+8. **Auto-discovery**: Which MD files to surface per project?
+9. **Performance**: 5 projects x (session + agents + terminals) = potentially many active panes
+
+---
+
+## Decisions Log
+
+| Decision | Rationale | Date |
+|---|---|---|
+| (pending adversarial review) | | |
+
+## Errors Encountered
+
+| Error | Cause | Fix | Date |
+|---|---|---|---|