review: the persona becomes the system-prompt plugin's deployment config

Review round 2 (tianyicui inline comments):

- dsh-system-prompt itself registers the harness:identity (-100) and
  deployment:persona (0) sections — they must survive a swapped loop
  plugin, so they leave dsh-agent-loop; the persona text is the plugin's
  own validated 'persona' config. The model/cwd variables STAY on the
  loop: runtime facts of the agents it drives.
- AgentOptions.systemPrompt is deleted with all its forwarding plumbing:
  the app configs' systemPrompt keys become 'persona' routed through
  dsh-agent-core (schema = z.intersect of the owners'), the ACP bridge
  and tool-subagent stop carrying persona configuration, and subagent
  children now render the deployment persona like every other agent.
- Example personas drop transport/interface trivia (ACP, CLI) — facts
  irrelevant to the model.
- Root CONTEXT.md removed (not idiomatic); its persona definition was
  wrong under the new ownership anyway.
- Docs, READMEs, the prompt-variables RFC, and generated catalogs
  updated; new loop test pins the assemble-waterfall escape valve
  (an emptied assembly sends NO system field).

packages/fs/tool-fs/tests/fs-tools.e2e.ts

@@ -32,10 +32,10 @@ const SYSTEM = 'You are a coding assistant. Use the write tool to create files,
 describe.skipIf(!process.env.DEEPSEEK_API_KEY)('fs tools with-key smoke', () => {
   it('creates, reads, then edits a file — verified on disk', async () => {
     workdir = await mkdtemp(join(tmpdir(), 'dsh-fs-e2e-'))
-    ctx = await fsHarness(workdir)
+    ctx = await fsHarness(workdir, SYSTEM)
     // agentLoop.create prepares a session with no cwd, so the provider default
     // (config.cwd = workdir) is the workspace.
-    const agent = ctx.agentLoop.create(AgentId('fs-e2e'), { model: 'deepseek-v4-flash', systemPrompt: SYSTEM })
+    const agent = ctx.agentLoop.create(AgentId('fs-e2e'), { model: 'deepseek-v4-flash' })
 
     agent.send([{ type: 'text', text:
       'Create a file named note.txt containing exactly the line: status: draft. '
@@ -63,12 +63,12 @@ describe.skipIf(!process.env.DEEPSEEK_API_KEY)('fs tools with-key smoke', () =>
     workdir = configDir
     const sessionDir = await mkdtemp(join(tmpdir(), 'dsh-fs-e2e-session-'))
     try {
-      ctx = await fsHarness(configDir)
+      ctx = await fsHarness(configDir, SYSTEM)
       const handle = ctx.agents.create({
         agentId: AgentId('fs-e2e-cwd'),
         sessionId: SessionId(`fs-e2e-cwd-${Date.now()}`),
         meta: { cwd: sessionDir },
-        agentOptions: { model: 'deepseek-v4-flash', systemPrompt: SYSTEM },
+        agentOptions: { model: 'deepseek-v4-flash' },
       })
       handle.agent.send([{ type: 'text', text:
         'Use the write tool to create a file named where.txt containing exactly the line: here. Tell me when done.' }])

packages/fs/tool-fs/tests/harness.ts

@@ -18,13 +18,14 @@ import * as LlmDeepSeek from '@deepseek-ai/dsh-llm-deepseek'
  *
  * `fsCwd` is the local backend's default base; a per-session cwd (set via a
  * session header) overrides it, but this harness creates agents without a
- * session cwd, so the provider default IS the workspace.
+ * session cwd, so the provider default IS the workspace. `persona` is the
+ * deployment persona (the system-prompt plugin's per-context config).
  */
-export async function fsHarness(fsCwd: string): Promise<Context> {
+export async function fsHarness(fsCwd: string, persona = ''): Promise<Context> {
   const ctx = new Context()
   await ctx.plugin(LlmService)
   await ctx.plugin(SessionStore)
-  await ctx.plugin(SystemPrompt)
+  await ctx.plugin(SystemPrompt, { persona })
   await ctx.plugin(ToolRegistry)
   await ctx.plugin(AgentRegistry)
   await ctx.plugin(AgentLoop, { agents: [] })

packages/fs/tool-fs/tests/tools.spec.ts

@@ -133,10 +133,11 @@ describe('registration', () => {
     // withdraw both, not just the schemas.
     expect(ctx.tools.schemas()).toHaveLength(3)
     const sectionNames = (a: { sections: { name: string }[] }) => a.sections.map(s => s.name).sort()
-    expect(sectionNames(await ctx.systemPrompt.assemble())).toEqual(['tool:edit', 'tool:read', 'tool:write'])
+    expect(sectionNames(await ctx.systemPrompt.assemble())).toEqual(['deployment:persona', 'harness:identity', 'tool:edit', 'tool:read', 'tool:write'])
     await fiber.dispose()
     expect(ctx.tools.schemas()).toHaveLength(0)
-    expect((await ctx.systemPrompt.assemble()).sections).toHaveLength(0)
+    // Only the system-prompt plugin's own built-in sections remain.
+    expect(sectionNames(await ctx.systemPrompt.assemble())).toEqual(['deployment:persona', 'harness:identity'])
   })
 })