Merge branch 'worktree-session-modes-rfc' (master: sandbox stack #169, skills #109, prompt snapshots #254)

The stack rebases onto a moved master through its base branch. Beyond
mechanical unions (both branches' demo scripts, example rows, service
roles, tool lists, acp deps, doc budgets — each side fit alone, the
union needs the higher ceilings), three semantic reconciliations:

- The ACP bridge now carries BOTH per-session surfaces: the sandbox
  stack's config options + approval answerer and this branch's session
  modes; session/new and session/load advertise modes AND configOptions
  side by side.
- The feature matrix supersedes the sandbox stance per the RFC's
  second-lander rule: session/set_mode and current_mode_update flip to
  shipped-by-dsh-mode, config-option rows stay as #169 wrote them, and
  §6 records both landed features under the picker-to-modes /
  knobs-to-config-options division.
- The snapshot pin grammar (#254: one header snapshot + declared deltas
  + a Markdown prompt golden) gains a symmetric declaration for what a
  delta cannot express: expectedHeaderSnapshots — a plan-mode flip
  resorts the canonical tool list, so its widening lands as a second
  full snapshot, now its own Markdown section. The pin-less-class and
  model-turn-only-pin amendments carry over; new fixtures cover the
  extended writer paths, and the plan-acp-agent scenarios re-recorded
  under the merged composition (the app now bundles the skill tool)
  with the suite's refresh mode wired through.

scripts/gen-tool-catalog.ts

@@ -48,13 +48,18 @@ import * as WebSearchExa from '@deepseek-ai/dsh-web-search-exa'
 import * as WebFetchLocal from '@deepseek-ai/dsh-web-fetch-local'
 import SubagentService from '@deepseek-ai/dsh-subagent'
 import * as SubagentMock from '@deepseek-ai/dsh-subagent-mock'
+import SkillService from '@deepseek-ai/dsh-skill'
+import * as SkillLocal from '@deepseek-ai/dsh-skill-local'
 import * as ToolAskUser from '@deepseek-ai/dsh-tool-ask-user'
 import * as ToolBash from '@deepseek-ai/dsh-tool-bash'
 import * as ToolCordis from '@deepseek-ai/dsh-tool-cordis'
 import * as ToolFs from '@deepseek-ai/dsh-tool-fs'
+import * as ToolSkill from '@deepseek-ai/dsh-tool-skill'
 import * as ToolTodo from '@deepseek-ai/dsh-tool-todo'
 import * as ToolSubagent from '@deepseek-ai/dsh-tool-subagent'
 import * as ToolWeb from '@deepseek-ai/dsh-tool-web'
+import VmWorkflowEngine from '@deepseek-ai/dsh-workflow-workerthread'
+import * as ToolWorkflow from '@deepseek-ai/dsh-tool-workflow'
 
 const root = resolve(import.meta.dirname, '..')
 const OUT = 'docs/tool-catalog.md'
@@ -191,6 +196,21 @@ const TOOL_PACKAGES: ToolPackage[] = [
     note:
       'The read-before-write/edit policy is added by `@deepseek-ai/dsh-fs-policy` (an `fs/*` event-gate plugin, no schema change); a deployment that loads these tools is expected to also load it. The tool schemas above are identical with or without the policy plugin.',
   },
+  {
+    pkg: '@deepseek-ai/dsh-tool-skill',
+    dir: 'tool-skill',
+    source: 'packages/skill/tool-skill/src/index.ts',
+    requires: ['ctx.tools', 'ctx.skills'],
+    writes: ['tool/call', 'tool/result'],
+    async mount(ctx) {
+      await ctx.plugin(SkillService)
+      await ctx.plugin(SkillLocal, {
+        dshHome: resolve(root, '.tmp/tool-catalog/.dsh'),
+        agentsHome: resolve(root, '.tmp/tool-catalog/.agents'),
+      })
+      await ctx.plugin(ToolSkill)
+    },
+  },
   {
     pkg: '@deepseek-ai/dsh-tool-subagent',
     dir: 'tool-subagent',
@@ -219,6 +239,22 @@ const TOOL_PACKAGES: ToolPackage[] = [
     note:
       'todo_write is session-owned state; UIs render the latest todo/write event as a checklist or ACP plan.',
   },
+  {
+    pkg: '@deepseek-ai/dsh-tool-workflow',
+    dir: 'tool-workflow',
+    source: 'packages/workflow/tool-workflow/src/index.ts',
+    requires: ['ctx.tools', 'ctx.workflows', 'ctx.systemPrompt', 'a calling Agent (exec.agent parents the script children)'],
+    writes: ['tool/call', 'tool/result'],
+    async mount(ctx) {
+      // The tool injects `workflows`; boot the vm engine over a scripted
+      // subagent provider to satisfy it. The schema does not depend on which
+      // provider backs the engine.
+      await ctx.plugin(SubagentService)
+      await ctx.plugin(SubagentMock, { name: 'mock' })
+      await ctx.plugin(VmWorkflowEngine, { provider: 'mock' })
+      await ctx.plugin(ToolWorkflow)
+    },
+  },
   {
     pkg: '@deepseek-ai/dsh-tool-web',
     dir: 'tool-web',