Expand plugin host surface (#5205)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The plugin system is the extension boundary for optional product
capabilities
> - Rich plugins need more than a worker entrypoint: they need scoped
database storage, local project folders, managed agents/routines, host
navigation, and reusable UI components
> - The LLM Wiki work exposed those missing host surfaces while keeping
plugin code outside the core control plane
> - This pull request expands the core plugin host, SDK, server APIs,
and UI bridge so plugins can declare and use those surfaces
> - The benefit is that future plugins can integrate with Paperclip
through documented, validated contracts instead of bespoke server or UI
imports

## What Changed

- Added plugin-managed database namespaces and migration tracking,
including Drizzle schema/migration files and SQL validation for
namespace isolation.
- Added server support for plugin local folders, managed agents, managed
routines, scoped plugin APIs, and plugin operation visibility.
- Expanded shared plugin manifest/types/validators and SDK
host/testing/UI exports for richer plugin surfaces.
- Added reusable UI pieces for file trees, managed routines, resizable
sidebars, route sidebars, and plugin bridge initialization.
- Updated plugin docs and example plugins to use the expanded host and
SDK surface.

## Verification

- `pnpm install --frozen-lockfile`
- `pnpm run preflight:workspace-links && pnpm exec vitest run
packages/shared/src/validators/plugin.test.ts
server/src/__tests__/plugin-database.test.ts
server/src/__tests__/plugin-local-folders.test.ts
server/src/__tests__/plugin-managed-agents.test.ts
server/src/__tests__/plugin-managed-routines.test.ts
server/src/__tests__/plugin-orchestration-apis.test.ts
ui/src/api/plugins.test.ts ui/src/components/FileTree.test.tsx
ui/src/components/ResizableSidebarPane.test.tsx
ui/src/pages/PluginPage.test.tsx ui/src/plugins/bridge.test.ts` passed:
11 files, 67 tests.
- Confirmed this PR changes 89 files and does not include
`pnpm-lock.yaml` or `.github/workflows/*`.

## Risks

- Medium: this expands plugin host contracts across db/shared/server/ui
and includes a new core migration (`0076_useful_elektra.sql`).
- The plugin database namespace validator is intentionally restrictive;
plugin authors may need follow-up affordances for SQL patterns that
remain blocked.
- Merge this before the LLM Wiki plugin PR so the plugin can resolve the
new SDK and host APIs.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5 coding agent, tool-enabled shell/git/GitHub
workflow. Context window size was not exposed by the runtime.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

packages/plugins/sdk/src/ui/index.ts

@@ -43,20 +43,89 @@
  * - `usePluginData(key, params)` — fetch data from the worker's `getData` handler
  * - `usePluginAction(key)` — get a callable that invokes the worker's `performAction` handler
  * - `useHostContext()` — read the current active company, project, entity, and user IDs
+ * - `useHostNavigation()` — navigate Paperclip-internal links through the host router
+ * - `useHostLocation()` — observe the current host pathname/search/hash for URL-driven UI
  * - `usePluginStream(channel)` — subscribe to real-time SSE events from the worker
  */
 export {
   usePluginData,
   usePluginAction,
   useHostContext,
+  useHostNavigation,
+  useHostLocation,
   usePluginStream,
   usePluginToast,
 } from "./hooks.js";
 
+export {
+  MetricCard,
+  StatusBadge,
+  DataTable,
+  TimeseriesChart,
+  MarkdownBlock,
+  MarkdownEditor,
+  KeyValueList,
+  ActionBar,
+  LogView,
+  JsonTree,
+  Spinner,
+  ErrorBoundary,
+  FileTree,
+  IssuesList,
+  AssigneePicker,
+  ProjectPicker,
+  ManagedRoutinesList,
+} from "./components.js";
+
+export type {
+  MetricTrend,
+  MetricCardProps,
+  StatusBadgeVariant,
+  StatusBadgeProps,
+  DataTableColumn,
+  DataTableProps,
+  TimeseriesDataPoint,
+  TimeseriesChartProps,
+  MarkdownBlockProps,
+  MarkdownEditorProps,
+  KeyValuePair,
+  KeyValueListProps,
+  ActionBarItem,
+  ActionBarProps,
+  LogViewEntry,
+  LogViewProps,
+  JsonTreeProps,
+  SpinnerProps,
+  ErrorBoundaryProps,
+  FileTreeNode,
+  FileTreeBadgeVariant,
+  FileTreeBadge,
+  FileTreeTone,
+  FileTreeEmptyState,
+  FileTreeErrorState,
+  FileTreePathCollection,
+  FileTreeProps,
+  IssuesListFilters,
+  IssuesListProps,
+  AssigneePickerSelection,
+  AssigneePickerProps,
+  ProjectPickerProps,
+  ManagedRoutineMissingRef,
+  ManagedRoutinesListAgent,
+  ManagedRoutinesListItem,
+  ManagedRoutinesListProject,
+  ManagedRoutinesListProps,
+} from "./components.js";
+
 // Bridge error and host context types
 export type {
   PluginBridgeError,
   PluginBridgeErrorCode,
+  HostNavigation,
+  HostNavigationOptions,
+  HostNavigationLinkOptions,
+  HostNavigationLinkProps,
+  HostLocation,
   PluginHostContext,
   PluginModalBoundsRequest,
   PluginRenderCloseEvent,
@@ -80,6 +149,7 @@ export type {
   PluginWidgetProps,
   PluginDetailTabProps,
   PluginSidebarProps,
+  PluginRouteSidebarProps,
   PluginProjectSidebarItemProps,
   PluginCommentAnnotationProps,
   PluginCommentContextMenuItemProps,