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>

package-lock.json

@@ -35406,6 +35406,7 @@
         "node-pty": "1.2.0-beta.11",
         "onnxruntime-node": "^1.23.0",
         "openai": "^4.20.0",
+        "p-limit": "^7.3.0",
         "pi-acp": "^0.0.24",
         "pino": "^10.2.0",
         "pino-pretty": "^13.1.3",
@@ -35681,6 +35682,21 @@
         "node": ">= 0.6"
       }
     },
+    "packages/server/node_modules/p-limit": {
+      "version": "7.3.0",
+      "resolved": "https://registry.npmjs.org/p-limit/-/p-limit-7.3.0.tgz",
+      "integrity": "sha512-7cIXg/Z0M5WZRblrsOla88S4wAK+zOQQWeBYfV3qJuJXMr+LnbYjaadrFaS0JILfEDPVqHyKnZ1Z/1d6J9VVUw==",
+      "license": "MIT",
+      "dependencies": {
+        "yocto-queue": "^1.2.1"
+      },
+      "engines": {
+        "node": ">=20"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "packages/server/node_modules/raw-body": {
       "version": "3.0.2",
       "resolved": "https://registry.npmjs.org/raw-body/-/raw-body-3.0.2.tgz",
@@ -35778,6 +35794,18 @@
         "node": ">= 0.6"
       }
     },
+    "packages/server/node_modules/yocto-queue": {
+      "version": "1.2.2",
+      "resolved": "https://registry.npmjs.org/yocto-queue/-/yocto-queue-1.2.2.tgz",
+      "integrity": "sha512-4LCcse/U2MHZ63HAJVE+v71o7yOdIe4cZ70Wpf8D/IyjDKYQLV5GD46B+hSTjJsvV5PztjvHoU580EftxjDZFQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=12.20"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/sindresorhus"
+      }
+    },
     "packages/server/node_modules/zod": {
       "version": "3.25.76",
       "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",