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>

server/src/services/plugin-registry.ts

@@ -3,6 +3,7 @@ import type { Db } from "@paperclipai/db";
 import {
   plugins,
   pluginConfig,
+  pluginCompanySettings,
   pluginEntities,
   pluginJobs,
   pluginJobRuns,
@@ -15,6 +16,7 @@ import type {
   UpdatePluginStatus,
   UpsertPluginConfig,
   PatchPluginConfig,
+  PluginCompanySettings,
   PluginEntityRecord,
   PluginEntityQuery,
   PluginJobRecord,
@@ -387,6 +389,64 @@ export function pluginRegistryService(db: Db) {
       return rows[0] ?? null;
     },
 
+    // ----- Company settings ----------------------------------------------
+
+    /** Retrieve company-scoped plugin settings. */
+    getCompanySettings: (pluginId: string, companyId: string): Promise<PluginCompanySettings | null> =>
+      db
+        .select()
+        .from(pluginCompanySettings)
+        .where(and(
+          eq(pluginCompanySettings.pluginId, pluginId),
+          eq(pluginCompanySettings.companyId, companyId),
+        ))
+        .then((rows) => rows[0] ?? null) as Promise<PluginCompanySettings | null>,
+
+    /** Create or replace company-scoped plugin settings. */
+    upsertCompanySettings: async (
+      pluginId: string,
+      companyId: string,
+      input: { enabled?: boolean; settingsJson: Record<string, unknown>; lastError?: string | null },
+    ): Promise<PluginCompanySettings> => {
+      const plugin = await getById(pluginId);
+      if (!plugin) throw notFound("Plugin not found");
+
+      const existing = await db
+        .select()
+        .from(pluginCompanySettings)
+        .where(and(
+          eq(pluginCompanySettings.pluginId, pluginId),
+          eq(pluginCompanySettings.companyId, companyId),
+        ))
+        .then((rows) => rows[0] ?? null);
+
+      if (existing) {
+        return db
+          .update(pluginCompanySettings)
+          .set({
+            enabled: input.enabled ?? existing.enabled,
+            settingsJson: input.settingsJson,
+            lastError: input.lastError ?? null,
+            updatedAt: new Date(),
+          })
+          .where(eq(pluginCompanySettings.id, existing.id))
+          .returning()
+          .then((rows) => rows[0]) as Promise<PluginCompanySettings>;
+      }
+
+      return db
+        .insert(pluginCompanySettings)
+        .values({
+          pluginId,
+          companyId,
+          enabled: input.enabled ?? true,
+          settingsJson: input.settingsJson,
+          lastError: input.lastError ?? null,
+        })
+        .returning()
+        .then((rows) => rows[0]) as Promise<PluginCompanySettings>;
+    },
+
     // ----- Entities -------------------------------------------------------
 
     /**