step 5 (complete): docs purge, fresh ARCHITECTURE + ROADMAP + CHANGELOG

Purged 29,966 lines of stale chat-switchboard documentation:
  - 41 docs/ files (ICD specs, design docs, archive, workflow docs)
  - 5 root MD files (CHANGESET, TURNOVER, ICD-DRIFT-AUDIT, etc.)

New documentation:
  - docs/ARCHITECTURE.md — kernel components, design principles, data layer
  - ROADMAP.md — v0.1.0 through v0.5.0 MVP with decision log
  - CHANGELOG.md — fresh, starting from v0.1.0 fork
  - README.md — rewritten for switchboard-core

Also in this commit:
  - config.go: stripped 7 dropped fields, DB default → switchboard_core
  - pages/loaders.go: stripped provider/model/notes/projects loaders
  - pages/pages.go: stripped persona store lookup
  - handlers/workflows.go: stripped persona tool grants
  - main.go: stripped team provider routes, avatar routes

Production code: zero references to deleted packages, stores, or models.
-29,966/+352 lines across 73 files.

ROADMAP.md

@@ -0,0 +1,84 @@
+# Switchboard Core — Roadmap
+
+## Current: v0.1.0 — The Kernel
+
+Fork of chat-switchboard, gutted to a pure extension platform. All AI/chat
+features removed from the kernel. What remains is the minimum viable
+platform that extensions build on.
+
+### Phase 0 (in progress)
+
+| Step | Status | Description |
+|------|--------|-------------|
+| 1. Module rename | ✅ | `chat-switchboard` → `switchboard-core` |
+| 2. Delete packages | ✅ | 15 Go packages, 29 handler files removed |
+| 3. Gut stores/models | ✅ | 40 → 20 store interfaces, kernel-only models |
+| 4. Fresh migrations | ✅ | 9 files × 2 dialects, 27 tables |
+| 5. Fix compilation | 🔧 | ~95% done, ~5 compile errors remaining |
+| 6. Fix tests | ⬜ | Prune 13K test lines to kernel-only |
+| 7. Frontend gut | ⬜ | Shell + SDK only, vendor libs baked |
+| 8. New ICD | ⬜ | Kernel-only API spec |
+| 9. CI/CD + Dockerfile | ⬜ | Single image, new DB names |
+| 10. Smoke test + tag | ⬜ | Deploy, verify, tag v0.1.0 |
+
+## v0.2.0 — SDK & Triggers
+
+The contract that extensions build against. Three trigger primitives,
+SDK stabilization, and the first rebuilt extension (tasks).
+
+- **Trigger system**: time (cron), webhook (inbound HTTP), event (bus subscription)
+- **Event bus subscriptions**: extensions register match expressions at install time
+- **SDK contract**: `sb.slots()`, `sb.actions`, `sb.api.ext()`, `sb.storage`
+- **Primitive UI components**: toast, confirm, prompt, dialog (stabilize existing)
+- **Theme tokens** exposed to extensions
+- **Task extension**: first proof-of-concept — full task system rebuilt as a
+  Starlark extension using triggers + ext_data + notifications
+
+## v0.3.0 — Editor Surface
+
+The code/markdown editor rebuilt as an installable surface package.
+Zero platform special-casing. Proves the full extension stack E2E.
+
+- Editor as `.pkg` archive
+- CM6 integration via surface viewport
+- File tree, tabs, preview pane — all extension-provided
+
+## v0.4.0 — Chat Extension
+
+The AI chat system rebuilt as an installable extension package.
+
+- Provider registry as extension (BYOK chain, model catalog)
+- Completion streaming via Starlark `provider.complete`
+- Personas as extension data
+- Channel/message storage via ext_data tables
+- Tool system as extension hooks
+
+## v0.5.0 — MVP
+
+Extension and operations tracks converge. First externally usable release.
+
+- Package registry (browse, install, update, uninstall)
+- Extension marketplace foundations
+- Health monitoring dashboard
+- Backup/restore tooling
+- Documentation site
+
+## Post-MVP
+
+- Rich media extensions: image generation, code sandbox, STT/TTS
+- Desktop app (Tauri or Electron)
+- Sidecar tier: container-based extensions
+- Federation: cross-instance package sharing
+- Plugin marketplace with signing and review
+
+## Design Decisions Log
+
+| Decision | Rationale |
+|----------|-----------|
+| Tasks → extension | Scheduler was the most entangled kernel component (~3,400 lines). Rebuilding as extension validates the trigger system and removes the worst compilation debt. Three trigger primitives (time, webhook, event) replace the monolithic scheduler. |
+| Sessions removed | Channel-based sessions coupled to deleted chat system. Workflow instances need new storage model — either ext_data tables or a dedicated kernel table. |
+| `chat_only` → `custom` | Stage mode `chat_only` implied chat as a kernel concept. Renamed to `custom` which delegates to a surface package, proving extension composability. |
+| Providers removed from kernel | Provider configs, model catalog, routing policies — all moved to extension track. Kernel provides credential storage (connections) and the Starlark `provider.complete` module as the interface. |
+| Kernel permissions simplified | From 16 chat-centric permissions to 6 platform permissions. Extensions define their own capability requirements in manifests. |
+| Preact+htm retained | 3KB runtime, no build step, works for extension authors without bundler config. KISS. |
+| Single Docker image | Drop the frontend/backend split. Go binary + assets + migrations in one image. Simpler deployment, fewer moving parts. |