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>

ui/src/pages/RoutineDetail.tsx

@@ -702,36 +702,44 @@ export function RoutineDetail() {
     <div className="max-w-2xl space-y-6">
       {/* Header: editable title + actions */}
       <div className="flex items-start gap-4">
-        <textarea
-          ref={titleInputRef}
-          className="flex-1 min-w-0 resize-none overflow-hidden bg-transparent text-xl font-bold outline-none placeholder:text-muted-foreground/50"
-          placeholder="Routine title"
-          rows={1}
-          value={editDraft.title}
-          onChange={(event) => {
-            setEditDraft((current) => ({ ...current, title: event.target.value }));
-            autoResizeTextarea(event.target);
-          }}
-          onKeyDown={(event) => {
-            if (event.key === "Enter" && !event.metaKey && !event.ctrlKey && !event.nativeEvent.isComposing) {
-              event.preventDefault();
-              descriptionEditorRef.current?.focus();
-              return;
-            }
-            if (event.key === "Tab" && !event.shiftKey) {
-              event.preventDefault();
-              if (editDraft.assigneeAgentId) {
-                if (editDraft.projectId) {
-                  descriptionEditorRef.current?.focus();
-                } else {
-                  projectSelectorRef.current?.focus();
-                }
-              } else {
-                assigneeSelectorRef.current?.focus();
+        <div className="min-w-0 flex-1 space-y-2">
+          <textarea
+            ref={titleInputRef}
+            className="w-full resize-none overflow-hidden bg-transparent text-xl font-bold outline-none placeholder:text-muted-foreground/50"
+            placeholder="Routine title"
+            rows={1}
+            value={editDraft.title}
+            onChange={(event) => {
+              setEditDraft((current) => ({ ...current, title: event.target.value }));
+              autoResizeTextarea(event.target);
+            }}
+            onKeyDown={(event) => {
+              if (event.key === "Enter" && !event.metaKey && !event.ctrlKey && !event.nativeEvent.isComposing) {
+                event.preventDefault();
+                descriptionEditorRef.current?.focus();
+                return;
               }
-            }
-          }}
-        />
+              if (event.key === "Tab" && !event.shiftKey) {
+                event.preventDefault();
+                if (editDraft.assigneeAgentId) {
+                  if (editDraft.projectId) {
+                    descriptionEditorRef.current?.focus();
+                  } else {
+                    projectSelectorRef.current?.focus();
+                  }
+                } else {
+                  assigneeSelectorRef.current?.focus();
+                }
+              }
+            }}
+          />
+          {routine.managedByPlugin ? (
+            <Badge variant="outline" className="gap-1 text-xs text-muted-foreground">
+              Managed by {routine.managedByPlugin.pluginDisplayName}
+              <span className="font-mono text-[10px]">{routine.managedByPlugin.resourceKey}</span>
+            </Badge>
+          ) : null}
+        </div>
         <div className="flex shrink-0 items-center gap-3 pt-1">
           <RunButton
             onClick={() => {