feat: GitHub service — scoped token minting and credential helper

[pranavpatilsce]

Summary

Adds a github reef service that gives agents programmatic access to the org's GitHub repositories via short-lived, scoped installation tokens. Uses the Vers API key (already injected into all VMs) to mint tokens through vers-landing's POST /api/github/installation-token endpoint (vers-landing PR #264).

Two layers:

• Credential helper (git-credential-vers) — transparent git clone/git push using full-org tokens, installed at build time on root and golden images
• Reef service (services/github/) — scoped tokens for in-repo work via API routes and reef_github_token tool

Also surfaces LLM errors (e.g. 429 no credits) in agent chat responses instead of showing blank output.

New files

File	Purpose
services/github/index.ts	ServiceModule — routes, tools, token cache, profiles
services/github/credential-helper.sh	Shell script for git credential protocol, reads VERS_API_KEY from env at runtime

Token profiles

Profile	Permissions	Use case
read	admin:read, contents:read, PRs:read, issues:read, checks:read, statuses:read, actions:read	Research, triage, review PRs, check CI
develop	admin:read, contents:write, PRs:write, issues:write, checks:read, statuses:read, actions:read	Full dev cycle — push branches, create PRs, monitor CI
clone	contents:read	Clone repos (credential helper preferred)
ci	actions:write, checks:read, statuses:read, contents:read	Trigger workflows, re-run checks, monitor results

Agents can also pass custom repositories and permissions for fine-grained control beyond profiles.

Behavioral guardrails

Enforced via tool descriptions injected into every agent (root + golden child VMs):

• Never delete repositories
• Never merge or push directly to main
• Always create pull requests and keep descriptions updated
• Use credential helper only for clone/create
• Use reef_github_token with scoped profiles for all in-repo work

Security

• No secrets in images — credential helper reads VERS_API_KEY from env at runtime
• Tokens are short-lived (~1 hour), cached in memory, auto-refreshed before expiry
• No profile grants administration:write — agents cannot delete repos

Routes

Method	Path	Description
POST	/github/token	Mint a scoped token (profile or custom permissions)
GET	/github/profiles	List available profiles
GET	/github/status	Integration status (configured, cached tokens)
GET	/github/_panel	HTML debug view

Verified end-to-end

Tested on a provisioned fleet against hdresearch/reef and hdresearch/vers-landing:

• ✅ read — list PRs, issues, workflow runs, branch protection
• ✅ develop — create branch, push commit, create/update PR, write comments
• ✅ ci — read check runs and workflow status
• ✅ Cross-repo tokens (reef + vers-landing in one session)
• ✅ PR lifecycle (create, update description, close, delete branch)

Companion PR

• vers-fleets — adds github to shared operational DNA, installs credential helper in root + golden image build scripts

Test plan

• Verify bun test passes (329 tests, 0 failures)
• Provision a fleet with --reef-path pointing to this branch
• Mint tokens via all 4 profiles, confirm permissions match
• Clone a repo using credential helper on the VM
• Create a test branch + PR using develop token, verify CI runs