Extract the shared in-process driver into dsh-subagent-inprocess (review feedback)

The shared run driver lived inside dsh-subagent-spawn, so the spawn package
carried fork-aware seeding logic and dsh-subagent-fork depended backward on
dsh-subagent-spawn — the two in-process backends were not independent.

Move the driver (startInProcessRun, depthOf, SubagentDepthError,
InProcessRunOptions) into a new pure-library package
@deepseek-ai/dsh-subagent-inprocess that registers nothing. spawn and fork now
both depend only on that driver and neither knows about the other; spawn no
longer re-exports it and fork no longer imports from spawn.

Also wire BOTH backends in examples/coding-agent/cordis.yml (config-only): load
dsh-subagent-spawn + dsh-subagent-fork + two dsh-tool-subagent instances with
distinct toolNames (subagent → spawn, subagent_fork → fork), demonstrating that
exposing multiple transports needs no code change.

packages/subagent/subagent-fork/package.json

@@ -23,7 +23,7 @@
     "@deepseek-ai/dsh-agent": "^0.0.1",
     "@deepseek-ai/dsh-session": "^0.0.1",
     "@deepseek-ai/dsh-subagent": "^0.0.1",
-    "@deepseek-ai/dsh-subagent-spawn": "^0.0.1",
+    "@deepseek-ai/dsh-subagent-inprocess": "^0.0.1",
     "cordis": "^4.0.0-rc.6"
   },
   "dependencies": {
@@ -36,6 +36,7 @@
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-subagent": "workspace:^",
+    "@deepseek-ai/dsh-subagent-inprocess": "workspace:^",
     "@deepseek-ai/dsh-subagent-spawn": "workspace:^",
     "@deepseek-ai/dsh-system-prompt": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",

packages/subagent/subagent-fork/src/index.ts

@@ -2,8 +2,10 @@
  * The in-process FORK subagent backend: registers a {@link SubagentProvider} on
  * `ctx.subagents` that runs each child as a child {@link Agent} SEEDED with a
  * prefix of the parent's session log — so the child inherits the parent's
- * conversation context instead of starting fresh. Shares the run driver with
- * `@deepseek-ai/dsh-subagent-spawn`; the only difference is the seed.
+ * conversation context instead of starting fresh. The run mechanics live in
+ * `@deepseek-ai/dsh-subagent-inprocess` ({@link startInProcessRun}); this
+ * backend just computes the seed. The spawn backend is an independent peer over
+ * the same driver.
  *
  * The seed boundary is the crux: at the moment a subagent tool's `execute`
  * runs, the parent's CURRENT turn is open and unbalanced (it holds the
@@ -23,7 +25,7 @@ import z from 'schemastery'
 import type { SessionEvent } from '@deepseek-ai/dsh-session'
 import type { Agent } from '@deepseek-ai/dsh-agent'
 import type { SubagentCapabilities, SubagentProvider, SubagentStartRequest } from '@deepseek-ai/dsh-subagent'
-import { startInProcessRun } from '@deepseek-ai/dsh-subagent-spawn'
+import { startInProcessRun } from '@deepseek-ai/dsh-subagent-inprocess'
 
 export const name = 'subagent-fork'
 export const inject = ['subagents', 'agents']

packages/subagent/subagent-fork/tsconfig.json

@@ -27,7 +27,7 @@
       "path": "../subagent"
     },
     {
-      "path": "../subagent-spawn"
+      "path": "../subagent-inprocess"
     }
   ]
 }