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/app/src/i18n/resources/en.ts

@@ -1854,8 +1854,6 @@ export const en = {
       metadata: {
         title: "Metadata generation",
         info: "Project-specific instructions injected into the AI prompts Paseo uses to generate metadata - use them to enforce your team's conventions like branch naming, commit style, or PR format",
-        agentTitle: "Agent titles",
-        agentTitlePlaceholder: "Keep titles imperative and under 40 characters",
         branchName: "Branch names",
         branchNamePlaceholder: "Prefix branches with feat/ or fix/, mb/ for personal branches",
         commitMessage: "Commit messages",