Support provider-owned fresh retry workspaces (#17252)

## Thinking Path

> - Paperclip coordinates AI agents and retains their work across
failures.
> - A retry can require a new workspace while preserving the failed
attempt.
> - Core rejects this recovery strategy for provider-owned storage.
> - Providers should implement the required outcome using their own
storage design.
> - This pull request adds a semantic fresh-preparation contract and
delegates recovery preparation.
> - The benefit is that a supported provider can run a fresh retry
without losing prior work.

## Linked Issues or Issue Description

**What happened?**
A retry that selects `fresh_isolated_workspace` fails with
`fresh_workspace_storage_unsupported` for provider-owned storage.

**Expected behavior**
Core asks a capable provider to prepare new storage and attach verified
recovery files. The failed workspace remains intact.

**Steps to reproduce**
Run a task in a task-capable plugin environment. Let the task fail
without a verified workspace preservation receipt. Retry the task so
Core selects a fresh attempt.

**Paperclip version or commit**
6204239cf (rebased on current master).

**Deployment mode**
Self-hosted server with a plugin task environment and managed workspace
provider.

Search found no duplicate implementation. This branch includes the
default-provider changes from #17247 and preserves their source
selection behavior.

## What Changed

- Define an opt-in fresh-preparation contract with a stable attempt
identity and verified recovery file descriptors.
- Describe retained-storage and recovery-attachment guarantees without
requiring a Git storage layout.
- Reserve replacement task bindings with revision checks and keep the
failed workspace intact. Projectless and project-backed task
environments both replay their stable attempt reservation.
- Reconcile an interrupted preparation against its reserved workspace
and stable operation identity.
- Stage verified recovery archives at stable transfer paths. Delegate
attachment materialization to the provider.
- Preserve projectless attempt directory identities through later turns
and pin the intent into each execution lease.
- Protect fresh intent and projectless ownership from caller metadata
replacement or injection.

## Verification

- SDK workspace-provider tests: 4 passed.
- Targeted reservation and task-dispatch tests: 31 passed.
- Recovery transfer staging and lifecycle focus: 7 passed. The separate
cache-cleanup failure reconciliation case also passed.
- After rebasing on current master, 7 focused preparation and ownership
cases passed. These cover inherited provider defaults, fresh
preparation, stable projectless identity, and authorization denial.
- The focused metadata authority regression passed, including forged
intent, replacement, and null metadata patches.
- Three assembled interrupted task-reservation cases passed:
projectless, project with a saved source, and project with a newly
selected default source.
- Targeted tests use worktree SDK sources. No full local build or
typecheck ran.
- Local checks remain targeted as requested. Latest-head GitHub CI
passed: 54 successful checks, including typecheck, build, server suites,
Runner validation, and E2E shards; 2 unrelated Storybook checks were
skipped.
- Greptile reviewed commit 73595b0c61 at
5/5 with zero unresolved threads.
- Live VM E2E has not run.

## Risks

- Existing providers retain their existing behavior. Fresh attempts
require explicit version support.
- The companion provider implementation must materialize recovery
snapshots safely and preserve the old workspace.
- Fresh retries require the companion provider implementation. Providers
without the version marker fail closed.

## Model Used

- OpenAI GPT-6.1 (`gpt-6.1-sol`), reasoning and coding tools. The
runtime does not expose the context-window limit.

## 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 searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

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

server/src/__tests__/environment-task-runtime.test.ts

@@ -4,7 +4,11 @@ import { executionWorkspaces, type Db } from "@paperclipai/db";
 import { environmentTaskOperationSchema, parseEnvironmentTaskResult } from "@paperclipai/plugin-sdk";
 import { executeEnvironmentTask } from "../services/environment-task-runtime.js";
 
-const state = vi.hoisted(() => ({ plugin: {} as any }));
+const state = vi.hoisted(() => ({ plugin: {} as any, release: vi.fn() }));
+vi.mock("../services/provider-fresh-workspace.js", () => ({
+  stageProviderFreshWorkspace: async (input: { existing: unknown }) => input.existing,
+  releaseProviderRecoveryTransfers: state.release,
+}));
 vi.mock("../services/plugin-registry.js", () => ({ pluginRegistryService: () => ({ getById: vi.fn(async () => state.plugin) }) }));
 const leaseId = "10000000-0000-4000-8000-000000000001";
 const projectId = "10000000-0000-4000-8000-000000000002";
@@ -30,9 +34,36 @@ function worker(result: unknown = { kind: "accepted", taskId: "attempt-1" }) {
 const submit = { kind: "submit" as const, preparedLaunchId: "configuration", projectIds: [projectId], runner: { protocolMin: 1, protocolMax: 2, harness: "codex", runnerId: "runner", leaseId, runId: "run", sessionId: "session", turnId: "turn", itemId: "item" }, bootstrapTicket: "transient-test-ticket" };
 
 beforeEach(() => {
+  state.release.mockReset();
   state.plugin = { id: "original", pluginKey: "test.provider", status: "ready", manifestJson: { capabilities: ["environment.drivers.register"], environmentDrivers: [{ driverKey: "tasks", supportsTasks: true }] } };
 });
 describe("plugin-provided Runner execution", () => {
+  it("forwards a retained fresh directory intent on later launch calls and checks provider support", async () => {
+    const value = row();
+    value.lease.metadata.runnerTaskProjectAuthValidation.projectIds = [];
+    const fresh = { attemptId: leaseId, sourceRunId: secondProjectId, previousWorkspaceId: null, recoverySnapshots: [] };
+    Object.assign(value.lease.metadata, { freshWorkspace: fresh });
+    Object.assign(state.plugin.manifestJson.environmentDrivers[0], { freshWorkspaceVersion: 1 });
+    const workers = worker();
+    await executeEnvironmentTask(database(value, []).db, workers as never, { companyId: "company", leaseId, operation: { ...submit, projectIds: [] } });
+    expect(workers.call).toHaveBeenCalledWith("original", "environmentTask", expect.objectContaining({ fresh }), 15_000);
+    delete state.plugin.manifestJson.environmentDrivers[0].freshWorkspaceVersion;
+    const denied = worker();
+    await expect(executeEnvironmentTask(database(value, []).db, denied as never, { companyId: "company", leaseId,
+      operation: { ...submit, projectIds: [] } })).rejects.toThrow("fresh workspace preparation unavailable");
+    expect(denied.call).not.toHaveBeenCalled();
+  });
+  it("releases fresh transfer copies only after confirmed task completion", async () => {
+    const value = row();
+    const fresh = { attemptId: leaseId, sourceRunId: secondProjectId, previousWorkspaceId: null, recoverySnapshots: [] };
+    Object.assign(value.lease.metadata, { freshWorkspace: fresh });
+    const workers = worker();
+    await executeEnvironmentTask(database(value).db, workers as never, { companyId: "company", leaseId, operation: { kind: "complete" } });
+    expect(state.release).not.toHaveBeenCalled();
+    Object.assign(value.lease.metadata, { runnerTaskExecutionStopped: true });
+    await executeEnvironmentTask(database(value).db, workers as never, { companyId: "company", leaseId, operation: { kind: "complete" } });
+    expect(state.release).toHaveBeenCalledWith("company", fresh);
+  });
   it("passes only the workspace binding pinned to this lease and provider", async () => {
     const value = row(); value.lease.metadata.runnerTaskProjectAuthValidation.projectIds = [];
     const binding = { pluginId: leaseId, projectId, executionWorkspaceId: secondProjectId, projectWorkspaceId: projectId,