Add sandbox environment support (#4415)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies.
> - The environment/runtime layer decides where agent work executes and
how the control plane reaches those runtimes.
> - Today Paperclip can run locally and over SSH, but sandboxed
execution needs a first-class environment model instead of one-off
adapter behavior.
> - We also want sandbox providers to be pluggable so the core does not
hardcode every provider implementation.
> - This branch adds the Sandbox environment path, the provider
contract, and a deterministic fake provider plugin.
> - That required synchronized changes across shared contracts, plugin
SDK surfaces, server runtime orchestration, and the UI
environment/workspace flows.
> - The result is that sandbox execution becomes a core control-plane
capability while keeping provider implementations extensible and
testable.

## What Changed

- Added sandbox runtime support to the environment execution path,
including runtime URL discovery, sandbox execution targeting,
orchestration, and heartbeat integration.
- Added plugin-provider support for sandbox environments so providers
can be supplied via plugins instead of hardcoded server logic.
- Added the fake sandbox provider plugin with deterministic behavior
suitable for local and automated testing.
- Updated shared types, validators, plugin protocol definitions, and SDK
helpers to carry sandbox provider and workspace-runtime contracts across
package boundaries.
- Updated server routes and services so companies can create sandbox
environments, select them for work, and execute work through the sandbox
runtime path.
- Updated the UI environment and workspace surfaces to expose sandbox
environment configuration and selection.
- Added test coverage for sandbox runtime behavior, provider seams,
environment route guards, orchestration, and the fake provider plugin.

## Verification

- Ran locally before the final fixture-only scrub:
  - `pnpm -r typecheck`
  - `pnpm test:run`
  - `pnpm build`
- Ran locally after the final scrub amend:
  - `pnpm vitest run server/src/__tests__/runtime-api.test.ts`
- Reviewer spot checks:
  - create a sandbox environment backed by the fake provider plugin
  - run work through that environment
- confirm sandbox provider execution does not inherit host secrets
implicitly

## Risks

- This touches shared contracts, plugin SDK plumbing, server runtime
orchestration, and UI environment/workspace flows, so regressions would
likely show up as cross-layer mismatches rather than isolated type
errors.
- Runtime URL discovery and sandbox callback selection are sensitive to
host/bind configuration; if that logic is wrong, sandbox-backed
callbacks may fail even when execution succeeds.
- The fake provider plugin is intentionally deterministic and
test-oriented; future providers may expose capability gaps that this
branch does not yet cover.

## Model Used

- OpenAI Codex coding agent on a GPT-5-class backend in the
Paperclip/Codex harness. Exact backend model ID is not exposed
in-session. Tool-assisted workflow with shell execution, file editing,
git history inspection, and local test execution.

## 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
- [ ] 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

server/src/services/activity.ts

@@ -4,6 +4,8 @@ import {
   activityLog,
   agents,
   documentRevisions,
+  environmentLeases,
+  environments,
   heartbeatRunEvents,
   heartbeatRuns,
   issueComments,
@@ -397,6 +399,7 @@ export function activityService(db: Db) {
           continuationAttempt: heartbeatRuns.continuationAttempt,
           lastUsefulActionAt: heartbeatRuns.lastUsefulActionAt,
           nextAction: heartbeatRuns.nextAction,
+          contextSnapshot: heartbeatRuns.contextSnapshot,
         })
         .from(heartbeatRuns)
         .innerJoin(
@@ -425,6 +428,8 @@ export function activityService(db: Db) {
         .orderBy(desc(heartbeatRuns.createdAt));
 
       if (runs.length === 0) return runs;
+      const runIds = runs.map((run) => run.runId);
+      if (runIds.length === 0) return runs;
 
       const exhaustionRows = await db
         .select({
@@ -434,7 +439,7 @@ export function activityService(db: Db) {
         .from(heartbeatRunEvents)
         .where(
           and(
-            inArray(heartbeatRunEvents.runId, runs.map((run) => run.runId)),
+            inArray(heartbeatRunEvents.runId, runIds),
             eq(heartbeatRunEvents.eventType, "lifecycle"),
             sql`${heartbeatRunEvents.message} like 'Bounded retry exhausted%'`,
           ),
@@ -447,10 +452,68 @@ export function activityService(db: Db) {
         retryExhaustedReasonByRunId.set(row.runId, row.message);
       }
 
-      return runs.map((run) => ({
-        ...run,
-        retryExhaustedReason: retryExhaustedReasonByRunId.get(run.runId) ?? null,
-      }));
+      const leaseRows = await db
+        .select({
+          lease: environmentLeases,
+          environment: {
+            id: environments.id,
+            name: environments.name,
+            driver: environments.driver,
+          },
+        })
+        .from(environmentLeases)
+        .innerJoin(environments, eq(environmentLeases.environmentId, environments.id))
+        .where(
+          and(
+            eq(environmentLeases.companyId, companyId),
+            inArray(environmentLeases.heartbeatRunId, runIds),
+          ),
+        )
+        .orderBy(desc(environmentLeases.lastUsedAt), desc(environmentLeases.createdAt));
+
+      const leaseByRunId = new Map<string, (typeof leaseRows)[number]>();
+      for (const row of leaseRows) {
+        if (row.lease.heartbeatRunId && !leaseByRunId.has(row.lease.heartbeatRunId)) {
+          leaseByRunId.set(row.lease.heartbeatRunId, row);
+        }
+      }
+
+      return runs.map((run) => {
+        const leaseRow = leaseByRunId.get(run.runId);
+        const leaseMetadata = leaseRow?.lease.metadata ?? null;
+        const workspacePath =
+          typeof leaseMetadata?.remoteCwd === "string" && leaseMetadata.remoteCwd.trim().length > 0
+            ? leaseMetadata.remoteCwd
+            : typeof leaseMetadata?.remoteWorkspacePath === "string" && leaseMetadata.remoteWorkspacePath.trim().length > 0
+              ? leaseMetadata.remoteWorkspacePath
+              : null;
+        return {
+          ...run,
+          environment: leaseRow
+            ? {
+                id: leaseRow.environment.id,
+                name: leaseRow.environment.name,
+                driver: leaseRow.environment.driver,
+              }
+            : null,
+          environmentLease: leaseRow
+            ? {
+                id: leaseRow.lease.id,
+                status: leaseRow.lease.status,
+                leasePolicy: leaseRow.lease.leasePolicy,
+                provider: leaseRow.lease.provider,
+                providerLeaseId: leaseRow.lease.providerLeaseId,
+                executionWorkspaceId: leaseRow.lease.executionWorkspaceId,
+                workspacePath,
+                failureReason: leaseRow.lease.failureReason,
+                cleanupStatus: leaseRow.lease.cleanupStatus,
+                acquiredAt: leaseRow.lease.acquiredAt,
+                releasedAt: leaseRow.lease.releasedAt,
+              }
+            : null,
+          retryExhaustedReason: retryExhaustedReasonByRunId.get(run.runId) ?? null,
+        };
+      });
     },
 
     issuesForRun: async (runId: string) => {