fix(server): centralize git subprocesses with p-limit throttling (#310)

* Fix uncaught timeout rejection when archiving agents

* fix(server): centralize git subprocesses under runGitCommand with p-limit throttling

Supersedes #299. Same problem (unbounded git subprocess concurrency causing
zombie accumulation), different approach: a single `runGitCommand(args, opts)`
function backed by `p-limit` instead of a custom semaphore pool.

- Always uses `spawn` (one code path, no exec/execFile split)
- Concurrency configurable via PASEO_GIT_CONCURRENCY env var (default 8)
- 30s default timeout for read-only ops, 120s for mutations
- Centralized error formatting, stdout truncation, process reaping
- Runtime tests verifying throttling, timeout kills, deadlock prevention

* fix: update lockfile signatures and Nix hash

* fix(server): add Windows compatibility to runGitCommand

- shell: true on Windows (resolves .cmd/.bat git shims)
- windowsHide: true always (prevents console window flashes)
- quoteForCmd for args with spaces when routing through cmd.exe
- Tests verify shell/windowsHide behavior per platform

* refactor: use spawnProcess instead of duplicating Windows handling

spawnProcess from spawn.ts already handles shell: true on Windows,
arg quoting for cmd.exe, and windowsHide: true. No need to reimplement.

* fix: non-null assertions for stdio streams in strict build

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

packages/app/src/components/agent-list.tsx

@@ -258,7 +258,8 @@ export function AgentList({
     if (!actionAgent || !actionClient) {
       return;
     }
-    void actionClient.archiveAgent(actionAgent.id);
+    // Timeout errors are swallowed — the daemon will still process the archive
+    void actionClient.archiveAgent(actionAgent.id).catch(() => {});
     setActionAgent(null);
   }, [actionAgent, actionClient]);
 

packages/app/src/screens/workspace/workspace-screen.tsx

@@ -1291,7 +1291,8 @@ function WorkspaceScreenContent({ serverId, workspaceId }: WorkspaceScreenProps)
           });
         }
 
-        void archiveAgent({ serverId: normalizedServerId, agentId });
+        // Errors (e.g. timeout) are handled by the mutation's onSettled callback
+        void archiveAgent({ serverId: normalizedServerId, agentId }).catch(() => {});
       });
     },
     [archiveAgent, closeTab, closeWorkspaceTabWithCleanup, normalizedServerId, persistenceKey],