Add AgentGit M1: agent-native git layer over a Forgejo backend

AgentGit is a thin, DID-gated source-collaboration layer over a backend
forge (default Forgejo at git.profullstack.com, BBS-members-only) — not a
new git host. M1 implements the contract and engines:

- forge/adapter.ts: ForgeAdapter interface (only forge-specific surface)
- forge/forgejo.ts: ForgejoAdapter over Forgejo/Gitea REST v1 (injectable
  fetch, typed errors), incl. ensureUser for member provisioning
- access.ts: gateAccess DID membership gate (owner/role/visibility)
- merge-policy.ts: evaluateMergePolicy pure engine (reviews, reputation
  floor, checks, escrow, merge method, agent-merge toggle)
- service.ts: AgentGitService ties gate + policy to the adapter; refuses
  policy-failing merges; provisionMember hook for AgentBBS
- schemas: logicsrc-repo + logicsrc-pull-request, registered in
  @logicsrc/validators with fixtures
- docs/agentgit.md spec; plugin wired into root build (default/disabled)

27 vitest tests pass; full monorepo build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/schemas/fixtures/pull-request.yaml

@@ -0,0 +1,24 @@
+type: logicsrc.pull_request
+version: "1.0"
+repo: agentgit-demo
+number: 7
+title: Add Forgejo backend adapter
+description: Implements the M1 ForgeAdapter against the Forgejo REST API.
+author_did: contributor.profullstack
+source_branch: feat/forgejo-adapter
+target_branch: main
+head_sha: abc1234
+task: task-42
+status: approved
+checks:
+  - name: ci
+    status: passing
+    url: https://git.profullstack.com/owner/agentgit-demo/actions
+reviews:
+  - reviewer_did: maintainer.profullstack
+    decision: approve
+    reputation: 25
+    summary: Looks good, policy-gated merge verified.
+    created_at: 2026-06-14T01:00:00Z
+created_at: 2026-06-14T00:30:00Z
+updated_at: 2026-06-14T01:05:00Z