feat: project-level prompts for metadata generation (#836)

* feat(server): project-level prompts for metadata generation

Add `metadataGeneration` config to `paseo.json` so projects can customize the
four LLM-generated metadata strings — agent title, worktree branch name, commit
message, and pull request title+body. Each entry takes an `instructions` string
that gets injected as a `<user-instructions>` block between the default rules
and the load-bearing JSON format contract, with wrapper text saying user
instructions override defaults. Missing/empty/invalid config keeps every prompt
byte-identical to today.

* refactor(server): centralize project metadata prompt building

Three near-identical readers and four gate-then-wrap blocks collapsed
into one buildMetadataPrompt helper. wrapWithUserInstructions tightened
to require a non-empty string; its misleading empty fallback is gone.

* feat(app): edit metadata generation prompts in project settings

Adds four textareas (agent title, branch name, commit message, pull
request) under project settings, modeled on the existing setup/teardown
pattern. Round-trips through paseo.json preserving unknown sibling
fields at both the metadataGeneration and entry level.

packages/server/src/server/agent/mcp-server.ts

@@ -79,7 +79,10 @@ export interface AgentMcpServerOptions {
   scheduleService?: ScheduleService | null;
   providerRegistry?: Record<AgentProvider, ProviderDefinition> | null;
   github?: GitHubService;
-  workspaceGitService?: Pick<WorkspaceGitService, "getSnapshot" | "listWorktrees">;
+  workspaceGitService?: Pick<
+    WorkspaceGitService,
+    "getSnapshot" | "listWorktrees" | "resolveRepoRoot"
+  >;
   archiveWorkspaceRecord?: ArchivePaseoWorktreeDependencies["archiveWorkspaceRecord"];
   emitWorkspaceUpdatesForWorkspaceIds?: ArchivePaseoWorktreeDependencies["emitWorkspaceUpdatesForWorkspaceIds"];
   markWorkspaceArchiving?: ArchivePaseoWorktreeDependencies["markWorkspaceArchiving"];
@@ -847,6 +850,7 @@ export async function createAgentMcpServer(options: AgentMcpServerOptions): Prom
         agentManager,
         agentId: snapshot.id,
         cwd: snapshot.cwd,
+        workspaceGitService: options.workspaceGitService,
         initialPrompt: trimmedPrompt,
         explicitTitle: snapshot.config.title,
         paseoHome: options.paseoHome,