Name agents by their first prompt line instead of an LLM summary (#1563)

* Name agents by their first prompt line instead of an LLM summary

The workspace title already captures the task; the LLM-generated agent
title just restated the same prompt. Drop the generator and keep the
provisional title (first prompt line), so the agent label stays
deterministic and explicit titles still win.

* Remove the no-op agent-title setting and leftover generator plumbing

Deleting the agent-title generator left its whole surface dangling: a
configurable "Agent titles" project setting that no longer did anything,
dead create-path plumbing, generator-only import/MCP deps, and the mock
provider's agent-title parser. Remove all of it, plus a dead test mock
and timing sleeps that guarded the deleted background job. Replace them
with a no-mock lifecycle test asserting the title stays the first prompt
line across create and settle.

Old paseo.json files with metadataGeneration.agentTitle still parse via
schema passthrough — see COMPAT(projectMetadataAgentTitle).

packages/protocol/src/paseo-config-schema.ts

@@ -39,11 +39,12 @@ export const PaseoMetadataGenerationEntrySchema = z
 
 export const PaseoMetadataGenerationSchema = z
   .object({
-    agentTitle: PaseoMetadataGenerationEntrySchema.optional(),
     branchName: PaseoMetadataGenerationEntrySchema.optional(),
     commitMessage: PaseoMetadataGenerationEntrySchema.optional(),
     pullRequest: PaseoMetadataGenerationEntrySchema.optional(),
   })
+  // COMPAT(projectMetadataAgentTitle): `agentTitle` project metadata prompts were removed
+  // in v0.1.96; keep legacy paseo.json parseable until 2026-12-16.
   .passthrough()
   .catch({});