Add Zopu dev bootstrap: git runtimes, Codex agent-os, dev agent

A vertical slice to bootstrap the product loop on the canonical zopu-code repo.

Primitives (packages/primitives, all tested + lint/type clean):
- GitRemoteRuntime: Gitea REST client (createIssue, createBranch,
  createPullRequest, listIssues, getIssue) as an Effect context service with
  a fetch-backed transport. Live-verified against puter/zopu-code.
- GitLocalRuntime: clone, addWorktree, commit, push, currentBranch,
  setRemoteUrl over a pluggable Shell (host subprocess now, AgentOS VM exec
  later). Tested against real temp git repos.
- agent-os: Codex support via @agentos-software/codex-cli — codexSoftware
  bundle (codex+git), makeCodexAgentOsConfig(), codexSessionEnv() for the
  OpenAI base URL/key.

Env:
- GITEA_URL/GITEA_TOKEN wired into convex.ts and convex.config.ts.
- .env.example documents the self-hosted git section.

Agents (packages/agents):
- zopu-dev: development agent that creates issues on the canonical repo and
  starts autonomous work runs. git-remote tools (create/list/branch/PR) wired
  to GitRemoteRuntime; start_workflow tool enqueues a work run.
- flue run zopu-dev verified live (lists/creates issues on real Gitea).

Backend (packages/backend):
- workflows.startIssueWork mutation: fetches a Gitea issue server-side and
  admits a queued work run. The Codex VM spawn body is the next step.

packages/env/src/convex.ts

@@ -7,6 +7,8 @@ export const env = createEnv({
   server: {
     CONVEX_SITE_URL: z.url(),
     FLUE_DB_TOKEN: z.string().min(1),
+    GITEA_TOKEN: z.string().min(1).optional(),
+    GITEA_URL: z.url().default("https://git.openputer.com"),
     NATIVE_APP_URL: z.string().min(1).default("code://"),
     SITE_URL: z.url(),
   },